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[taler-donau] branch master updated: reimported httpd keys files


From: gnunet
Subject: [taler-donau] branch master updated: reimported httpd keys files
Date: Thu, 11 Jan 2024 02:05:11 +0100

This is an automated email from the git hooks/post-receive script.

johannes-casaburi pushed a commit to branch master
in repository donau.

The following commit(s) were added to refs/heads/master by this push:
     new 4fc8dc9  reimported httpd keys files
4fc8dc9 is described below

commit 4fc8dc919a1b0758080549367d581143cf373ca2
Author: Casaburi Johannes <johannes.casaburi@students.bfh.ch>
AuthorDate: Thu Jan 11 02:02:31 2024 +0100

    reimported httpd keys files
---
 src/donau/donau-httpd_keys.c | 3007 ++++++++++++++++++++++++++++++------------
 src/donau/donau-httpd_keys.h |  416 ++++--
 2 files changed, 2507 insertions(+), 916 deletions(-)

diff --git a/src/donau/donau-httpd_keys.c b/src/donau/donau-httpd_keys.c
index 6558bfc..545aa63 100644
--- a/src/donau/donau-httpd_keys.c
+++ b/src/donau/donau-httpd_keys.c
@@ -1,13 +1,13 @@
 /*
    This file is part of TALER
-   Copyright (C) 2020-2024 Taler Systems SA
+   Copyright (C) 2024 Taler Systems SA
 
    TALER is free software; you can redistribute it and/or modify it under the
    terms of the GNU Affero General Public License as published by the Free 
Software
    Foundation; either version 3, or (at your option) any later version.
 
    TALER is distributed in the hope that it will be useful, but WITHOUT ANY
-   WARRANTY; without even the implied warranty of CHARITYABILITY or FITNESS FOR
+   WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS 
FOR
    A PARTICULAR PURPOSE.  See the GNU Affero General Public License for more 
details.
 
    You should have received a copy of the GNU Affero General Public License 
along with
@@ -16,16 +16,20 @@
 /**
  * @file donau-httpd_keys.c
  * @brief management of our various keys
- * @author Christian Grothoff
- * @author Özgür Kesim
+ * @author Johannes Casaburi
  */
 #include "taler/platform.h"
 #include "taler/taler_json_lib.h"
 #include "taler/taler_mhd_lib.h"
+//#include "taler/taler_kyclogic_lib.h"
+#include "taler/taler_dbevents.h"
 #include "donau-httpd.h"
-#include "donau-httpd_keys.h"
 #include "donau-httpd_config.h"
+#include "donau-httpd_keys.h"
+//#include "donau-httpd_responses.h"
 #include "donaudb_plugin.h"
+//#include "taler/taler_extensions.h"
+
 
 /**
  * How many /keys request do we hold in suspension at
@@ -33,155 +37,15 @@
  */
 #define SKR_LIMIT 32
 
+
 /**
  * When do we forcefully timeout a /keys request?
  */
 #define KEYS_TIMEOUT GNUNET_TIME_UNIT_MINUTES
 
-/**
- * Number of entries in the @e skr_head DLL.
- */
-static unsigned int skr_size;
-
-/**
- * Handle to a connection that should be force-resumed
- * with a hard error due to @a skr_size hitting
- * #SKR_LIMIT.
- */
-static struct MHD_Connection *skr_connection;
-
-/**
- * Entry of /keys requests that are currently suspended because we are
- * waiting for /keys to become ready.
- */
-struct SuspendedKeysRequests
-{
-  /**
-   * Kept in a DLL.
-   */
-  struct SuspendedKeysRequests *next;
-
-  /**
-   * Kept in a DLL.
-   */
-  struct SuspendedKeysRequests *prev;
-
-  /**
-   * The suspended connection.
-   */
-  struct MHD_Connection *connection;
-
-  /**
-   * When does this request timeout?
-   */
-  struct GNUNET_TIME_Absolute timeout;
-};
-
-/**
- * Head of DLL of suspended /keys requests.
- */
-static struct SuspendedKeysRequests *skr_head;
-
-/**
- * Tail of DLL of suspended /keys requests.
- */
-static struct SuspendedKeysRequests *skr_tail;
-
-/**
- * Task to force timeouts on /keys requests.
- */
-static struct GNUNET_SCHEDULER_Task *keys_tt;
-
-/**
- * Are we shutting down?
- */
-static bool terminating;
-
-/**
- * Function called to forcefully resume suspended keys requests.
- *
- * @param cls unused, NULL
- */
-static void
-keys_timeout_cb (void *cls)
-{
-  struct SuspendedKeysRequests *skr;
-
-  (void) cls;
-  keys_tt = NULL;
-  while (NULL != (skr = skr_head))
-  {
-    if (GNUNET_TIME_absolute_is_future (skr->timeout))
-      break;
-    GNUNET_log (GNUNET_ERROR_TYPE_INFO,
-                "Resuming /keys request due to timeout\n");
-    GNUNET_CONTAINER_DLL_remove (skr_head,
-                                 skr_tail,
-                                 skr);
-    MHD_resume_connection (skr->connection);
-    TALER_MHD_daemon_trigger ();
-    GNUNET_free (skr);
-  }
-  if (NULL == skr)
-    return;
-  keys_tt = GNUNET_SCHEDULER_add_at (skr->timeout,
-                                     &keys_timeout_cb,
-                                     NULL);
-}
-
-
-/**
- * Suspend /keys request while we (hopefully) are waiting to be
- * provisioned with key material.
- *
- * @param[in] connection to suspend
- */
-static MHD_RESULT
-suspend_request (struct MHD_Connection *connection)
-{
-  struct SuspendedKeysRequests *skr;
-
-  GNUNET_log (GNUNET_ERROR_TYPE_INFO,
-              "Suspending /keys request until key material changes\n");
-  if (terminating)
-  {
-    return TALER_MHD_reply_with_error (connection,
-                                       MHD_HTTP_INTERNAL_SERVER_ERROR,
-                                       TALER_EC_EXCHANGE_GENERIC_KEYS_MISSING,
-                                       "Exchange terminating");
-  }
-  skr = GNUNET_new (struct SuspendedKeysRequests);
-  skr->connection = connection;
-  MHD_suspend_connection (connection);
-  GNUNET_CONTAINER_DLL_insert (skr_head,
-                               skr_tail,
-                               skr);
-  skr->timeout = GNUNET_TIME_relative_to_absolute (KEYS_TIMEOUT);
-  if (NULL == keys_tt)
-  {
-    keys_tt = GNUNET_SCHEDULER_add_at (skr->timeout,
-                                       &keys_timeout_cb,
-                                       NULL);
-  }
-  skr_size++;
-  if (skr_size > SKR_LIMIT)
-  {
-    skr = skr_tail;
-    GNUNET_CONTAINER_DLL_remove (skr_head,
-                                 skr_tail,
-                                 skr);
-    skr_size--;
-    skr_connection = skr->connection;
-    MHD_resume_connection (skr->connection);
-    TALER_MHD_daemon_trigger ();
-    GNUNET_free (skr);
-  }
-  return MHD_YES;
-}
-
 
 /**
- * Information about a donation unit on offer by the donation unit helper.
+ * Information about a donation_unit on offer by the donation_unit helper.
  */
 struct HelperDonationUnit
 {
@@ -198,10 +62,15 @@ struct HelperDonationUnit
   struct GNUNET_TIME_Relative validity_duration;
 
   /**
-   * Hash of the full donation unit key.
+   * Hash of the full donation_unit key.
    */
   struct DONAU_DonationUnitHashP h_donation_unit_pub;
 
+  /**
+   * Signature over this key from the security module's key.
+   */
+  struct TALER_SecurityModuleSignatureP sm_sig;
+
   /**
    * The (full) public key.
    */
@@ -226,73 +95,134 @@ struct HelperDonationUnit
   } h_details;
 
   /**
-   * Name in configuration section for this donation unit type.
+   * Name in configuration section for this donation_unit type.
    */
   char *section_name;
 
 
 };
 
+
 /**
- * Information about a signing key on offer by the sign helper.
+ * Information about a signing key on offer by the esign helper.
  */
 struct HelperSignkey
 {
   /**
    * When will the helper start to use this key for signing?
    */
-  // struct GNUNET_TIME_Timestamp start_time;
-  int year;
+  struct GNUNET_TIME_Timestamp start_time;
+
+  /**
+   * For how long will the helper allow signing? 0 if
+   * the key was revoked or purged.
+   */
+  struct GNUNET_TIME_Relative validity_duration;
 
   /**
    * The public key.
    */
   struct DONAU_DonauPublicKeyP donau_pub;
 
+  /**
+   * Signature over this key from the security module's key.
+   */
+  struct TALER_SecurityModuleSignatureP sm_sig;
+
 };
 
-/**
- * Counter incremented whenever we have a reason to re-build the keys because
- * something external changed.  See #DH_keys_get_state() and
- * #DH_keys_update_states() for uses of this variable.
- */
-static uint64_t key_generation;
 
 /**
- * RSA security module public key, all zero if not known.
+ * State associated with the crypto helpers / security modules.  NOT updated
+ * when the #key_generation is updated (instead constantly kept in sync
+ * whenever #DH_keys_get_state() is called).
  */
-// static struct TALER_SecurityModulePublicKeyP donation_unit_rsa_sm_pub;
+struct HelperState
+{
 
-/**
- * CS security module public key, all zero if not known.
- */
-// static struct TALER_SecurityModulePublicKeyP donation_unit_cs_sm_pub;
+  /**
+   * Handle for the esign/EdDSA helper.
+   */
+  struct TALER_CRYPTO_DonauSignHelper *esh;
 
-/**
- * EdDSA security module public key, all zero if not known.
- */
-// static struct TALER_SecurityModulePublicKeyP esign_sm_pub;
+  /**
+   * Handle for the donation_unit/RSA helper.
+   */
+  struct TALER_CRYPTO_RsaDonationUnitHelper *rsadh;
 
+  /**
+   * Handle for the donation_unit/CS helper.
+   */
+  struct TALER_CRYPTO_CsDonationUnitHelper *csdh;
+
+  /**
+   * Map from H(donation_unit_pub) to `struct HelperDonationUnit` entries.
+   */
+  struct GNUNET_CONTAINER_MultiHashMap *donation_unit_keys;
+
+  /**
+   * Map from H(rsa_pub) to `struct HelperDonationUnit` entries.
+   */
+  struct GNUNET_CONTAINER_MultiHashMap *rsa_keys;
+
+  /**
+   * Map from H(cs_pub) to `struct HelperDonationUnit` entries.
+   */
+  struct GNUNET_CONTAINER_MultiHashMap *cs_keys;
+
+  /**
+   * Map from `struct DONAU_DonauPublicKey` to `struct HelperSignkey`
+   * entries.  Based on the fact that a `struct GNUNET_PeerIdentity` is also
+   * an EdDSA public key.
+   */
+  struct GNUNET_CONTAINER_MultiPeerMap *esign_keys;
+
+};
 
-/**
- * When do we forcefully timeout a /keys request?
- */
-#define KEYS_TIMEOUT GNUNET_TIME_UNIT_MINUTES
 
 /**
- * Stores the latest generation of our key state.
+ * Entry in (sorted) array with possible pre-build responses for /keys.
+ * We keep pre-build responses for the various (valid) cherry-picking
+ * values around.
  */
-static struct DH_KeyStateHandle *key_state;
+struct KeysResponseData
+{
+
+  /**
+   * Response to return if the client supports (deflate) compression.
+   */
+  struct MHD_Response *response_compressed;
+
+  /**
+   * Response to return if the client does not support compression.
+   */
+  struct MHD_Response *response_uncompressed;
+
+  /**
+   * ETag for these responses.
+   */
+  char *etag;
+
+  /**
+   * Cherry-picking timestamp the client must have set for this
+   * response to be valid.  0 if this is the "full" response.
+   * The client's request must include this date or a higher one
+   * for this response to be applicable.
+   */
+  struct GNUNET_TIME_Timestamp cherry_pick_date;
+
+};
+
 
 /**
- * @brief All information about an donau online signing key (which is used to
- * sign messages from the donau).
+ * @brief All information about an exchange online signing key (which is used 
to
+ * sign messages from the exchange).
  */
 struct SigningKey
 {
 
   /**
-   * The donau's (online signing) public key.
+   * The exchange's (online signing) public key.
    */
   struct DONAU_DonauPublicKeyP donau_pub;
 
@@ -301,16 +231,17 @@ struct SigningKey
    */
   struct DONAUDB_SignkeyMetaData meta;
 
+
 };
 
 struct DH_KeyStateHandle
 {
 
   /**
-   * Mapping from donation unit keys to donation unit key issue struct.
+   * Mapping from donation_unit keys to donation_unit key issue struct.
    * Used to lookup the key by hash.
    */
-  struct GNUNET_CONTAINER_MultiHashMap *denomkey_map;
+  struct GNUNET_CONTAINER_MultiHashMap *donation_unitkey_map;
 
   /**
    * Map from `struct DONAU_DonauPublicKey` to `struct SigningKey`
@@ -353,6 +284,12 @@ struct DH_KeyStateHandle
    */
   struct GNUNET_TIME_Timestamp reload_time;
 
+  /**
+   * What is the period at which we rotate keys
+   * (signing or donation_unit keys)?
+   */
+  struct GNUNET_TIME_Relative rekey_frequency;
+
   /**
    * When does our online signing key expire and we
    * thus need to re-generate this response?
@@ -367,102 +304,981 @@ struct DH_KeyStateHandle
 
 };
 
+
 /**
- * Entry in (sorted) array with possible pre-build responses for /keys.
- * We keep pre-build responses for the various (valid) cherry-picking
- * values around.
+ * Entry of /keys requests that are currently suspended because we are
+ * waiting for /keys to become ready.
  */
-struct KeysResponseData
+struct SuspendedKeysRequests
 {
-
   /**
-   * Response to return if the client supports (deflate) compression.
+   * Kept in a DLL.
    */
-  struct MHD_Response *response_compressed;
+  struct SuspendedKeysRequests *next;
 
   /**
-   * Response to return if the client does not support compression.
+   * Kept in a DLL.
    */
-  struct MHD_Response *response_uncompressed;
+  struct SuspendedKeysRequests *prev;
 
   /**
-   * ETag for these responses.
+   * The suspended connection.
    */
-  char *etag;
+  struct MHD_Connection *connection;
 
   /**
-   * Cherry-picking timestamp the client must have set for this
-   * response to be valid.  0 if this is the "full" response.
-   * The client's request must include this date or a higher one
-   * for this response to be applicable.
+   * When does this request timeout?
    */
-  struct GNUNET_TIME_Timestamp cherry_pick_date;
-
+  struct GNUNET_TIME_Absolute timeout;
 };
 
+
 /**
- * State associated with the crypto helpers / security modules.  NOT updated
- * when the #key_generation is updated (instead constantly kept in sync
- * whenever #DH_keys_get_state() is called).
+ * Stores the latest generation of our key state.
  */
-struct HelperState
+static struct DH_KeyStateHandle *key_state;
+
+/**
+ * Counter incremented whenever we have a reason to re-build the keys because
+ * something external changed.  See #DH_keys_get_state() and
+ * #DH_keys_update_states() for uses of this variable.
+ */
+static uint64_t key_generation;
+
+/**
+ * Handler listening for wire updates by other exchange
+ * services.
+ */
+static struct GNUNET_DB_EventHandler *keys_eh;
+
+/**
+ * Head of DLL of suspended /keys requests.
+ */
+static struct SuspendedKeysRequests *skr_head;
+
+/**
+ * Tail of DLL of suspended /keys requests.
+ */
+static struct SuspendedKeysRequests *skr_tail;
+
+/**
+ * Number of entries in the @e skr_head DLL.
+ */
+static unsigned int skr_size;
+
+/**
+ * Handle to a connection that should be force-resumed
+ * with a hard error due to @a skr_size hitting
+ * #SKR_LIMIT.
+ */
+static struct MHD_Connection *skr_connection;
+
+/**
+ * Task to force timeouts on /keys requests.
+ */
+static struct GNUNET_SCHEDULER_Task *keys_tt;
+
+/**
+ * For how long should a signing key be legally retained?
+ * Configuration value.
+ */
+static struct GNUNET_TIME_Relative signkey_legal_duration;
+
+/**
+ * What type of asset are we dealing with here?
+ */
+static char *asset_type;
+
+/**
+ * RSA security module public key, all zero if not known.
+ */
+static struct TALER_SecurityModulePublicKeyP donation_unit_rsa_sm_pub;
+
+/**
+ * CS security module public key, all zero if not known.
+ */
+static struct TALER_SecurityModulePublicKeyP donation_unit_cs_sm_pub;
+
+/**
+ * EdDSA security module public key, all zero if not known.
+ */
+static struct TALER_SecurityModulePublicKeyP esign_sm_pub;
+
+/**
+ * Are we shutting down?
+ */
+static bool terminating;
+
+
+
+/**
+ * Function called to forcefully resume suspended keys requests.
+ *
+ * @param cls unused, NULL
+ */
+static void
+keys_timeout_cb (void *cls)
 {
+  struct SuspendedKeysRequests *skr;
 
-  /**
-   * Handle for the esign/EdDSA helper.
-   */
-  struct TALER_CRYPTO_ExchangeSignHelper *esh;
+  (void) cls;
+  keys_tt = NULL;
+  while (NULL != (skr = skr_head))
+  {
+    if (GNUNET_TIME_absolute_is_future (skr->timeout))
+      break;
+    GNUNET_log (GNUNET_ERROR_TYPE_INFO,
+                "Resuming /keys request due to timeout\n");
+    GNUNET_CONTAINER_DLL_remove (skr_head,
+                                 skr_tail,
+                                 skr);
+    MHD_resume_connection (skr->connection);
+    TALER_MHD_daemon_trigger ();
+    GNUNET_free (skr);
+  }
+  if (NULL == skr)
+    return;
+  keys_tt = GNUNET_SCHEDULER_add_at (skr->timeout,
+                                     &keys_timeout_cb,
+                                     NULL);
+}
 
-  /**
-   * Handle for the donation_unit/RSA helper.
-   */
-  struct TALER_CRYPTO_RsaDenominationHelper *rsadh;
 
-  /**
-   * Handle for the donation_unit/CS helper.
-   */
-  struct TALER_CRYPTO_CsDenominationHelper *csdh;
+/**
+ * Suspend /keys request while we (hopefully) are waiting to be
+ * provisioned with key material.
+ *
+ * @param[in] connection to suspend
+ */
+static MHD_RESULT
+suspend_request (struct MHD_Connection *connection)
+{
+  struct SuspendedKeysRequests *skr;
 
-  /**
-   * Map from H(donation_unit_pub) to `struct HelperDenomination` entries.
-   */
-  struct GNUNET_CONTAINER_MultiHashMap *donation_unit_keys;
+  GNUNET_log (GNUNET_ERROR_TYPE_INFO,
+              "Suspending /keys request until key material changes\n");
+  if (terminating)
+  {
+    return TALER_MHD_reply_with_error (connection,
+                                       MHD_HTTP_INTERNAL_SERVER_ERROR,
+                                       TALER_EC_EXCHANGE_GENERIC_KEYS_MISSING,
+                                       "Donau terminating");
+  }
+  skr = GNUNET_new (struct SuspendedKeysRequests);
+  skr->connection = connection;
+  MHD_suspend_connection (connection);
+  GNUNET_CONTAINER_DLL_insert (skr_head,
+                               skr_tail,
+                               skr);
+  skr->timeout = GNUNET_TIME_relative_to_absolute (KEYS_TIMEOUT);
+  if (NULL == keys_tt)
+  {
+    keys_tt = GNUNET_SCHEDULER_add_at (skr->timeout,
+                                       &keys_timeout_cb,
+                                       NULL);
+  }
+  skr_size++;
+  if (skr_size > SKR_LIMIT)
+  {
+    skr = skr_tail;
+    GNUNET_CONTAINER_DLL_remove (skr_head,
+                                 skr_tail,
+                                 skr);
+    skr_size--;
+    skr_connection = skr->connection;
+    MHD_resume_connection (skr->connection);
+    TALER_MHD_daemon_trigger ();
+    GNUNET_free (skr);
+  }
+  return MHD_YES;
+}
 
-  /**
-   * Map from H(rsa_pub) to `struct HelperDenomination` entries.
-   */
-  struct GNUNET_CONTAINER_MultiHashMap *rsa_keys;
 
-  /**
-   * Map from H(cs_pub) to `struct HelperDenomination` entries.
-   */
-  struct GNUNET_CONTAINER_MultiHashMap *cs_keys;
+/**
+ * Called on each donation_unit key. Checks that the key still works.
+ *
+ * @param cls NULL
+ * @param hc donation_unit hash (unused)
+ * @param value a `struct DH_DonationUnitKey`
+ * @return #GNUNET_OK
+ */
+static enum GNUNET_GenericReturnValue
+check_dk (void *cls,
+          const struct GNUNET_HashCode *hc,
+          void *value)
+{
+  struct DH_DonationUnitKey *dk = value;
+
+  (void) cls;
+  (void) hc;
+  switch (dk->donation_unit_pub.bsign_pub_key->cipher)
+  {
+  case GNUNET_CRYPTO_BSA_INVALID:
+    break;
+  case GNUNET_CRYPTO_BSA_RSA:
+    GNUNET_assert (GNUNET_CRYPTO_rsa_public_key_check (
+                     
dk->donation_unit_pub.bsign_pub_key->details.rsa_public_key));
+    return GNUNET_OK;
+  case GNUNET_CRYPTO_BSA_CS:
+    /* nothing to do for GNUNET_CRYPTO_BSA_CS */
+    return GNUNET_OK;
+  }
+  GNUNET_assert (0);
+  return GNUNET_SYSERR;
+}
+
+
+void
+DH_check_invariants ()
+{
+  struct DH_KeyStateHandle *ksh;
+
+  //if (0 == DH_check_invariants_flag)
+  //  return;
+  ksh = DH_keys_get_state ();
+  if (NULL == ksh)
+    return;
+  GNUNET_CONTAINER_multihashmap_iterate (ksh->donation_unitkey_map,
+                                         &check_dk,
+                                         NULL);
+}
+
+
+void
+DH_resume_keys_requests (bool do_shutdown)
+{
+  struct SuspendedKeysRequests *skr;
+
+  if (do_shutdown)
+    terminating = true;
+  while (NULL != (skr = skr_head))
+  {
+    GNUNET_CONTAINER_DLL_remove (skr_head,
+                                 skr_tail,
+                                 skr);
+    skr_size--;
+    MHD_resume_connection (skr->connection);
+    TALER_MHD_daemon_trigger ();
+    GNUNET_free (skr);
+  }
+}
+
+
+/**
+ * Clear memory for responses to "/keys" in @a ksh.
+ *
+ * @param[in,out] ksh key state to update
+ */
+static void
+clear_response_cache (struct DH_KeyStateHandle *ksh)
+{
+  for (unsigned int i = 0; i<ksh->krd_array_length; i++)
+  {
+    struct KeysResponseData *krd = &ksh->krd_array[i];
+
+    MHD_destroy_response (krd->response_compressed);
+    MHD_destroy_response (krd->response_uncompressed);
+    GNUNET_free (krd->etag);
+  }
+  GNUNET_array_grow (ksh->krd_array,
+                     ksh->krd_array_length,
+                     0);
+}
+
+
+/**
+ * Check that the given RSA security module's public key is the one
+ * we have pinned.  If it does not match, we die hard.
+ *
+ * @param sm_pub RSA security module public key to check
+ */
+static void
+check_donation_unit_rsa_sm_pub (const struct TALER_SecurityModulePublicKeyP 
*sm_pub)
+{
+  if (0 !=
+      GNUNET_memcmp (sm_pub,
+                     &donation_unit_rsa_sm_pub))
+  {
+    if (! GNUNET_is_zero (&donation_unit_rsa_sm_pub))
+    {
+      GNUNET_log (GNUNET_ERROR_TYPE_ERROR,
+                  "Our RSA security module changed its key. This must not 
happen.\n");
+      GNUNET_assert (0);
+    }
+    donation_unit_rsa_sm_pub = *sm_pub; /* TOFU ;-) */
+  }
+}
+
+
+/**
+ * Check that the given CS security module's public key is the one
+ * we have pinned.  If it does not match, we die hard.
+ *
+ * @param sm_pub RSA security module public key to check
+ */
+static void
+check_donation_unit_cs_sm_pub (const struct TALER_SecurityModulePublicKeyP 
*sm_pub)
+{
+  if (0 !=
+      GNUNET_memcmp (sm_pub,
+                     &donation_unit_cs_sm_pub))
+  {
+    if (! GNUNET_is_zero (&donation_unit_cs_sm_pub))
+    {
+      GNUNET_log (GNUNET_ERROR_TYPE_ERROR,
+                  "Our CS security module changed its key. This must not 
happen.\n");
+      GNUNET_assert (0);
+    }
+    donation_unit_cs_sm_pub = *sm_pub; /* TOFU ;-) */
+  }
+}
+
+
+/**
+ * Check that the given EdDSA security module's public key is the one
+ * we have pinned.  If it does not match, we die hard.
+ *
+ * @param sm_pub EdDSA security module public key to check
+ */
+static void
+check_esign_sm_pub (const struct TALER_SecurityModulePublicKeyP *sm_pub)
+{
+  if (0 !=
+      GNUNET_memcmp (sm_pub,
+                     &esign_sm_pub))
+  {
+    if (! GNUNET_is_zero (&esign_sm_pub))
+    {
+      GNUNET_log (GNUNET_ERROR_TYPE_ERROR,
+                  "Our EdDSA security module changed its key. This must not 
happen.\n");
+      GNUNET_assert (0);
+    }
+    esign_sm_pub = *sm_pub; /* TOFU ;-) */
+  }
+}
+
+
+/**
+ * Helper function for #destroy_key_helpers to free all entries
+ * in the `donation_unit_keys` map.
+ *
+ * @param cls the `struct HelperDonationUnit`
+ * @param h_donation_unit_pub hash of the donation_unit public key
+ * @param value the `struct HelperDonationUnit` to release
+ * @return #GNUNET_OK (continue to iterate)
+ */
+static enum GNUNET_GenericReturnValue
+free_donation_unit_cb (void *cls,
+               const struct GNUNET_HashCode *h_donation_unit_pub,
+               void *value)
+{
+  struct HelperDonationUnit *hd = value;
+
+  (void) cls;
+  (void) h_donation_unit_pub;
+  //DONAU_donation_unit_pub_free (&hd->donation_unit_pub);
+  GNUNET_free (hd->section_name);
+  GNUNET_free (hd);
+  return GNUNET_OK;
+}
+
+
+/**
+ * Helper function for #destroy_key_helpers to free all entries
+ * in the `esign_keys` map.
+ *
+ * @param cls the `struct HelperSignkey`
+ * @param pid unused, matches the exchange public key
+ * @param value the `struct HelperSignkey` to release
+ * @return #GNUNET_OK (continue to iterate)
+ */
+static enum GNUNET_GenericReturnValue
+free_esign_cb (void *cls,
+               const struct GNUNET_PeerIdentity *pid,
+               void *value)
+{
+  struct HelperSignkey *hsk = value;
+
+  (void) cls;
+  (void) pid;
+  GNUNET_free (hsk);
+  return GNUNET_OK;
+}
+
+
+/**
+ * Destroy helper state. Does NOT call free() on @a hs, as that
+ * state is not separately allocated!  Dual to #setup_key_helpers().
+ *
+ * @param[in] hs helper state to free, but NOT the @a hs pointer itself!
+ */
+static void
+destroy_key_helpers (struct HelperState *hs)
+{
+  GNUNET_CONTAINER_multihashmap_iterate (hs->donation_unit_keys,
+                                         &free_donation_unit_cb,
+                                         hs);
+  GNUNET_CONTAINER_multihashmap_destroy (hs->rsa_keys);
+  hs->rsa_keys = NULL;
+  GNUNET_CONTAINER_multihashmap_destroy (hs->cs_keys);
+  hs->cs_keys = NULL;
+  GNUNET_CONTAINER_multihashmap_destroy (hs->donation_unit_keys);
+  hs->donation_unit_keys = NULL;
+  GNUNET_CONTAINER_multipeermap_iterate (hs->esign_keys,
+                                         &free_esign_cb,
+                                         hs);
+  GNUNET_CONTAINER_multipeermap_destroy (hs->esign_keys);
+  hs->esign_keys = NULL;
+  if (NULL != hs->rsadh)
+  {
+    TALER_CRYPTO_helper_rsa_disconnect (hs->rsadh);
+    hs->rsadh = NULL;
+  }
+  if (NULL != hs->csdh)
+  {
+    TALER_CRYPTO_helper_cs_disconnect (hs->csdh);
+    hs->csdh = NULL;
+  }
+  if (NULL != hs->esh)
+  {
+    TALER_CRYPTO_helper_esign_disconnect (hs->esh);
+    hs->esh = NULL;
+  }
+}
+
+
+/**
+ * Function called with information about available keys for signing.  Usually
+ * only called once per key upon connect. Also called again in case a key is
+ * being revoked, in that case with an @a end_time of zero.
+ *
+ * @param cls closure with the `struct HelperState *`
+ * @param section_name name of the donation_unit type in the configuration;
+ *                 NULL if the key has been revoked or purged
+ * @param start_time when does the key become available for signing;
+ *                 zero if the key has been revoked or purged
+ * @param validity_duration how long does the key remain available for signing;
+ *                 zero if the key has been revoked or purged
+ * @param h_rsa hash of the @a donation_unit_pub that is available (or was 
purged)
+ * @param bs_pub the public key itself, NULL if the key was revoked or purged
+ * @param sm_pub public key of the security module, NULL if the key was 
revoked or purged
+ * @param sm_sig signature from the security module, NULL if the key was 
revoked or purged
+ *               The signature was already verified against @a sm_pub.
+ */
+static void
+helper_rsa_cb (
+  void *cls,
+  const char *section_name,
+  struct GNUNET_TIME_Timestamp start_time,
+  struct GNUNET_TIME_Relative validity_duration,
+  const struct TALER_RsaPubHashP *h_rsa,
+  struct GNUNET_CRYPTO_BlindSignPublicKey *bs_pub,
+  const struct TALER_SecurityModulePublicKeyP *sm_pub,
+  const struct TALER_SecurityModuleSignatureP *sm_sig)
+{
+  struct HelperState *hs = cls;
+  struct HelperDonationUnit *hd;
+
+  GNUNET_log (GNUNET_ERROR_TYPE_INFO,
+              "RSA helper announces key %s for donation_unit type %s with 
validity %s\n",
+              GNUNET_h2s (&h_rsa->hash),
+              section_name,
+              GNUNET_STRINGS_relative_time_to_string (validity_duration,
+                                                      GNUNET_NO));
+  key_generation++;
+  DH_resume_keys_requests (false);
+  hd = GNUNET_CONTAINER_multihashmap_get (hs->rsa_keys,
+                                          &h_rsa->hash);
+  if (NULL != hd)
+  {
+    /* should be just an update (revocation!), so update existing entry */
+    hd->validity_duration = validity_duration;
+    return;
+  }
+  GNUNET_assert (NULL != sm_pub);
+  check_donation_unit_rsa_sm_pub (sm_pub);
+  hd = GNUNET_new (struct HelperDonationUnit);
+  hd->start_time = start_time;
+  hd->validity_duration = validity_duration;
+  hd->h_details.h_rsa = *h_rsa;
+  hd->sm_sig = *sm_sig;
+  GNUNET_assert (GNUNET_CRYPTO_BSA_RSA == bs_pub->cipher);
+  hd->donation_unit_pub.bsign_pub_key =
+    GNUNET_CRYPTO_bsign_pub_incref (bs_pub);
+  //DONAU_donation_unit_pub_hash (&hd->donation_unit_pub,
+  //                      &hd->h_donation_unit_pub);
+  hd->section_name = GNUNET_strdup (section_name);
+  GNUNET_assert (
+    GNUNET_OK ==
+    GNUNET_CONTAINER_multihashmap_put (
+      hs->donation_unit_keys,
+      &hd->h_donation_unit_pub.hash,
+      hd,
+      GNUNET_CONTAINER_MULTIHASHMAPOPTION_UNIQUE_ONLY));
+  GNUNET_assert (
+    GNUNET_OK ==
+    GNUNET_CONTAINER_multihashmap_put (
+      hs->rsa_keys,
+      &hd->h_details.h_rsa.hash,
+      hd,
+      GNUNET_CONTAINER_MULTIHASHMAPOPTION_UNIQUE_ONLY));
+}
+
+
+/**
+ * Function called with information about available CS keys for signing. 
Usually
+ * only called once per key upon connect. Also called again in case a key is
+ * being revoked, in that case with an @a end_time of zero.
+ *
+ * @param cls closure with the `struct HelperState *`
+ * @param section_name name of the donation_unit type in the configuration;
+ *                 NULL if the key has been revoked or purged
+ * @param start_time when does the key become available for signing;
+ *                 zero if the key has been revoked or purged
+ * @param validity_duration how long does the key remain available for signing;
+ *                 zero if the key has been revoked or purged
+ * @param h_cs hash of the @a donation_unit_pub that is available (or was 
purged)
+ * @param bs_pub the public key itself, NULL if the key was revoked or purged
+ * @param sm_pub public key of the security module, NULL if the key was 
revoked or purged
+ * @param sm_sig signature from the security module, NULL if the key was 
revoked or purged
+ *               The signature was already verified against @a sm_pub.
+ */
+static void
+helper_cs_cb (
+  void *cls,
+  const char *section_name,
+  struct GNUNET_TIME_Timestamp start_time,
+  struct GNUNET_TIME_Relative validity_duration,
+  const struct TALER_CsPubHashP *h_cs,
+  struct GNUNET_CRYPTO_BlindSignPublicKey *bs_pub,
+  const struct TALER_SecurityModulePublicKeyP *sm_pub,
+  const struct TALER_SecurityModuleSignatureP *sm_sig)
+{
+  struct HelperState *hs = cls;
+  struct HelperDonationUnit *hd;
+
+  GNUNET_log (GNUNET_ERROR_TYPE_INFO,
+              "CS helper announces key %s for donation_unit type %s with 
validity %s\n",
+              GNUNET_h2s (&h_cs->hash),
+              section_name,
+              GNUNET_STRINGS_relative_time_to_string (validity_duration,
+                                                      GNUNET_NO));
+  key_generation++;
+  DH_resume_keys_requests (false);
+  hd = GNUNET_CONTAINER_multihashmap_get (hs->cs_keys,
+                                          &h_cs->hash);
+  if (NULL != hd)
+  {
+    /* should be just an update (revocation!), so update existing entry */
+    hd->validity_duration = validity_duration;
+    return;
+  }
+  GNUNET_assert (NULL != sm_pub);
+  check_donation_unit_cs_sm_pub (sm_pub);
+  hd = GNUNET_new (struct HelperDonationUnit);
+  hd->start_time = start_time;
+  hd->validity_duration = validity_duration;
+  hd->h_details.h_cs = *h_cs;
+  hd->sm_sig = *sm_sig;
+  GNUNET_assert (GNUNET_CRYPTO_BSA_CS == bs_pub->cipher);
+  hd->donation_unit_pub.bsign_pub_key
+    = GNUNET_CRYPTO_bsign_pub_incref (bs_pub);
+  //DONAU_donation_unit_pub_hash (&hd->donation_unit_pub,
+  //                      &hd->h_donation_unit_pub);
+  hd->section_name = GNUNET_strdup (section_name);
+  GNUNET_assert (
+    GNUNET_OK ==
+    GNUNET_CONTAINER_multihashmap_put (
+      hs->donation_unit_keys,
+      &hd->h_donation_unit_pub.hash,
+      hd,
+      GNUNET_CONTAINER_MULTIHASHMAPOPTION_UNIQUE_ONLY));
+  GNUNET_assert (
+    GNUNET_OK ==
+    GNUNET_CONTAINER_multihashmap_put (
+      hs->cs_keys,
+      &hd->h_details.h_cs.hash,
+      hd,
+      GNUNET_CONTAINER_MULTIHASHMAPOPTION_UNIQUE_ONLY));
+}
+
+
+/**
+ * Function called with information about available keys for signing.  Usually
+ * only called once per key upon connect. Also called again in case a key is
+ * being revoked, in that case with an @a end_time of zero.
+ *
+ * @param cls closure with the `struct HelperState *`
+ * @param start_time when does the key become available for signing;
+ *                 zero if the key has been revoked or purged
+ * @param validity_duration how long does the key remain available for signing;
+ *                 zero if the key has been revoked or purged
+ * @param donau_pub the public key itself, NULL if the key was revoked or 
purged
+ * @param sm_pub public key of the security module, NULL if the key was 
revoked or purged
+ * @param sm_sig signature from the security module, NULL if the key was 
revoked or purged
+ *               The signature was already verified against @a sm_pub.
+ */
+static void
+helper_esign_cb (
+  void *cls,
+  struct GNUNET_TIME_Timestamp start_time,
+  struct GNUNET_TIME_Relative validity_duration,
+  const struct DONAU_DonauPublicKeyP *donau_pub,
+  const struct TALER_SecurityModulePublicKeyP *sm_pub,
+  const struct TALER_SecurityModuleSignatureP *sm_sig)
+{
+  struct HelperState *hs = cls;
+  struct HelperSignkey *hsk;
+  struct GNUNET_PeerIdentity pid;
+
+  GNUNET_log (GNUNET_ERROR_TYPE_INFO,
+              "EdDSA helper announces signing key %s with validity %s\n",
+              TALER_B2S (donau_pub),
+              GNUNET_STRINGS_relative_time_to_string (validity_duration,
+                                                      GNUNET_NO));
+  key_generation++;
+  DH_resume_keys_requests (false);
+  pid.public_key = donau_pub->eddsa_pub;
+  hsk = GNUNET_CONTAINER_multipeermap_get (hs->esign_keys,
+                                           &pid);
+  if (NULL != hsk)
+  {
+    /* should be just an update (revocation!), so update existing entry */
+    hsk->validity_duration = validity_duration;
+    return;
+  }
+  GNUNET_assert (NULL != sm_pub);
+  check_esign_sm_pub (sm_pub);
+  hsk = GNUNET_new (struct HelperSignkey);
+  hsk->start_time = start_time;
+  hsk->validity_duration = validity_duration;
+  hsk->donau_pub = *donau_pub;
+  hsk->sm_sig = *sm_sig;
+  GNUNET_assert (
+    GNUNET_OK ==
+    GNUNET_CONTAINER_multipeermap_put (
+      hs->esign_keys,
+      &pid,
+      hsk,
+      GNUNET_CONTAINER_MULTIHASHMAPOPTION_UNIQUE_ONLY));
+}
+
+
+/**
+ * Setup helper state.
+ *
+ * @param[out] hs helper state to initialize
+ * @return #GNUNET_OK on success
+ */
+static enum GNUNET_GenericReturnValue
+setup_key_helpers (struct HelperState *hs)
+{
+  hs->donation_unit_keys
+    = GNUNET_CONTAINER_multihashmap_create (1024,
+                                            GNUNET_YES);
+  hs->rsa_keys
+    = GNUNET_CONTAINER_multihashmap_create (1024,
+                                            GNUNET_YES);
+  hs->cs_keys
+    = GNUNET_CONTAINER_multihashmap_create (1024,
+                                            GNUNET_YES);
+  hs->esign_keys
+    = GNUNET_CONTAINER_multipeermap_create (32,
+                                            GNUNET_NO /* MUST BE NO! */);
+  hs->rsadh = TALER_CRYPTO_helper_rsa_connect (DH_cfg,
+                                               "taler",
+                                               &helper_rsa_cb,
+                                               hs);
+  if (NULL == hs->rsadh)
+  {
+    destroy_key_helpers (hs);
+    return GNUNET_SYSERR;
+  }
+  hs->csdh = TALER_CRYPTO_helper_cs_connect (DH_cfg,
+                                             "taler",
+                                             &helper_cs_cb,
+                                             hs);
+  if (NULL == hs->csdh)
+  {
+    destroy_key_helpers (hs);
+    return GNUNET_SYSERR;
+  }
+  hs->esh = TALER_CRYPTO_helper_esign_connect (DH_cfg,
+                                               "taler",
+                                               &helper_esign_cb,
+                                               hs);
+  if (NULL == hs->esh)
+  {
+    destroy_key_helpers (hs);
+    return GNUNET_SYSERR;
+  }
+  return GNUNET_OK;
+}
+
+
+/**
+ * Synchronize helper state. Polls the key helper for updates.
+ *
+ * @param[in,out] hs helper state to synchronize
+ */
+static void
+sync_key_helpers (struct HelperState *hs)
+{
+  TALER_CRYPTO_helper_rsa_poll (hs->rsadh);
+  TALER_CRYPTO_helper_cs_poll (hs->csdh);
+  TALER_CRYPTO_helper_esign_poll (hs->esh);
+}
+
+
+/**
+ * Free donation_unit key data.
+ *
+ * @param cls a `struct DH_KeyStateHandle`, unused
+ * @param h_donation_unit_pub hash of the donation_unit public key, unused
+ * @param value a `struct DH_DonationUnitKey` to free
+ * @return #GNUNET_OK (continue to iterate)
+ */
+static enum GNUNET_GenericReturnValue
+clear_donation_unit_cb (void *cls,
+                       const struct GNUNET_HashCode *h_donation_unit_pub,
+                       void *value)
+{
+  struct DH_DonationUnitKey *dk = value;
+
+  (void) cls;
+  (void) h_donation_unit_pub;
+  //DONAU_donation_unit_pub_free (&dk->donation_unit_pub);
+
+  GNUNET_free (dk);
+  return GNUNET_OK;
+}
+
+
+/**
+ * Free donation_unit key data.
+ *
+ * @param cls a `struct DH_KeyStateHandle`, unused
+ * @param pid the online signing key (type-disguised), unused
+ * @param value a `struct SigningKey` to free
+ * @return #GNUNET_OK (continue to iterate)
+ */
+static enum GNUNET_GenericReturnValue
+clear_signkey_cb (void *cls,
+                  const struct GNUNET_PeerIdentity *pid,
+                  void *value)
+{
+  struct SigningKey *sk = value;
+
+  (void) cls;
+  (void) pid;
+  GNUNET_free (sk);
+  return GNUNET_OK;
+}
+
+
+/**
+ * Free resources associated with @a cls, possibly excluding
+ * the helper data.
+ *
+ * @param[in] ksh key state to release
+ * @param free_helper true to also release the helper state
+ */
+static void
+destroy_key_state (struct DH_KeyStateHandle *ksh,
+                   bool free_helper)
+{
+
+  clear_response_cache (ksh);
+
+  GNUNET_CONTAINER_multihashmap_iterate (ksh->donation_unitkey_map,
+                                         &clear_donation_unit_cb,
+                                         ksh);
+  GNUNET_CONTAINER_multihashmap_destroy (ksh->donation_unitkey_map);
+  GNUNET_CONTAINER_multipeermap_iterate (ksh->signkey_map,
+                                         &clear_signkey_cb,
+                                         ksh);
+  GNUNET_CONTAINER_multipeermap_destroy (ksh->signkey_map);
+  if (free_helper)
+  {
+    destroy_key_helpers (ksh->helpers);
+    GNUNET_free (ksh->helpers);
+  }
+  if (NULL != ksh->management_keys_reply)
+  {
+    json_decref (ksh->management_keys_reply);
+    ksh->management_keys_reply = NULL;
+  }
+  GNUNET_free (ksh);
+}
+
+
+/**
+ * Function called whenever another exchange process has updated
+ * the keys data in the database.
+ *
+ * @param cls NULL
+ * @param extra unused
+ * @param extra_size number of bytes in @a extra unused
+ */
+static void
+keys_update_event_cb (void *cls,
+                      const void *extra,
+                      size_t extra_size)
+{
+  (void) cls;
+  (void) extra;
+  (void) extra_size;
+  GNUNET_log (GNUNET_ERROR_TYPE_INFO,
+              "Received /keys update event\n");
+  DH_check_invariants ();
+  key_generation++;
+  DH_resume_keys_requests (false);
+  DH_check_invariants ();
+}
+
+
+enum GNUNET_GenericReturnValue
+DH_keys_init ()
+{
+  struct GNUNET_DB_EventHeaderP es = {
+    .size = htons (sizeof (es)),
+    .type = htons (TALER_DBEVENT_EXCHANGE_KEYS_UPDATED),
+  };
+
+  if (GNUNET_OK !=
+      GNUNET_CONFIGURATION_get_value_time (DH_cfg,
+                                           "exchange",
+                                           "SIGNKEY_LEGAL_DURATION",
+                                           &signkey_legal_duration))
+  {
+    GNUNET_log_config_missing (GNUNET_ERROR_TYPE_ERROR,
+                               "exchange",
+                               "SIGNKEY_LEGAL_DURATION");
+    return GNUNET_SYSERR;
+  }
+  if (GNUNET_OK !=
+      GNUNET_CONFIGURATION_get_value_string (DH_cfg,
+                                             "exchange",
+                                             "ASSET_TYPE",
+                                             &asset_type))
+  {
+    GNUNET_log_config_missing (GNUNET_ERROR_TYPE_WARNING,
+                               "exchange",
+                               "ASSET_TYPE");
+    asset_type = GNUNET_strdup ("fiat");
+  }
+  keys_eh = DH_plugin->event_listen (DH_plugin->cls,
+                                      GNUNET_TIME_UNIT_FOREVER_REL,
+                                      &es,
+                                      &keys_update_event_cb,
+                                      NULL);
+  if (NULL == keys_eh)
+  {
+    GNUNET_break (0);
+    return GNUNET_SYSERR;
+  }
+  return GNUNET_OK;
+}
+
+
+/**
+ * Fully clean up our state.
+ */
+void
+DH_keys_finished ()
+{
+  if (NULL != keys_tt)
+  {
+    GNUNET_SCHEDULER_cancel (keys_tt);
+    keys_tt = NULL;
+  }
+  if (NULL != key_state)
+    destroy_key_state (key_state,
+                       true);
+  if (NULL != keys_eh)
+  {
+    DH_plugin->event_listen_cancel (DH_plugin->cls,
+                                     keys_eh);
+    keys_eh = NULL;
+  }
+}
+
 
-  /**
-   * Map from `struct TALER_ExchangePublicKey` to `struct HelperSignkey`
-   * entries.  Based on the fact that a `struct GNUNET_PeerIdentity` is also
-   * an EdDSA public key.
-   */
-  struct GNUNET_CONTAINER_MultiPeerMap *esign_keys;
+/**
+ * Function called with information about the exchange's donation_unit keys.
+ *
+ * @param cls closure with a `struct DH_KeyStateHandle *`
+ * @param donation_unit_pub public key of the donation_unit
+ * @param h_donation_unit_pub hash of @a donation_unit_pub
+ * @param meta meta data information about the donation_unit type (value, 
expirations, fees)
+ *        coins of this donation_unit
+ */
+static void
+donation_unit_info_cb (
+  void *cls,
+  const struct DONAU_DonationUnitPublicKey *donation_unit_pub,
+  const struct DONAU_DonationUnitHashP *h_donation_unit_pub,
+  const struct DONAUDB_DonationUnitKeyMetaData *meta)
+{
+  struct DH_KeyStateHandle *ksh = cls;
+  struct DH_DonationUnitKey *dk;
+
+  GNUNET_assert (GNUNET_CRYPTO_BSA_INVALID !=
+                 donation_unit_pub->bsign_pub_key->cipher);
+  //if (GNUNET_TIME_absolute_is_zero (meta->start.abs_time) ||
+  //    GNUNET_TIME_absolute_is_zero (meta->expire_withdraw.abs_time) ||
+  //    GNUNET_TIME_absolute_is_zero (meta->expire_deposit.abs_time) ||
+  //    GNUNET_TIME_absolute_is_zero (meta->expire_legal.abs_time) )
+  //{
+  //  GNUNET_log (GNUNET_ERROR_TYPE_ERROR,
+  //              "Database contains invalid donation_unit key %s\n",
+  //              GNUNET_h2s (&h_donation_unit_pub->hash));
+  //  return;
+  //}
+  dk = GNUNET_new (struct DH_DonationUnitKey);
+  DONAU_donation_unit_pub_deep_copy (&dk->donation_unit_pub,
+                             donation_unit_pub);
+  dk->h_donation_unit_pub = *h_donation_unit_pub;
+  //dk->meta = *meta;
+
+  GNUNET_assert (
+    GNUNET_OK ==
+    GNUNET_CONTAINER_multihashmap_put (ksh->donation_unitkey_map,
+                                       &dk->h_donation_unit_pub.hash,
+                                       dk,
+                                       
GNUNET_CONTAINER_MULTIHASHMAPOPTION_UNIQUE_ONLY));
+}
 
-};
 
 /**
- * Closure for #add_donation_unit_key_cb.
+ * Function called with information about the exchange's online signing keys.
+ *
+ * @param cls closure with a `struct DH_KeyStateHandle *`
+ * @param donau_pub the public key
+ * @param meta meta data information about the donation_unit type (expirations)
  */
-struct DonationUnitKeyCtx
+static void
+signkey_info_cb (
+  void *cls,
+  const struct DONAU_DonauPublicKeyP *donau_pub,
+  const struct DONAUDB_SignkeyMetaData *meta)
 {
-  /**
-   * Heap for sorting active donation unit keys by start time.
-   */
-  struct GNUNET_CONTAINER_Heap *heap;
+  struct DH_KeyStateHandle *ksh = cls;
+  struct SigningKey *sk;
+  struct GNUNET_PeerIdentity pid;
+
+  sk = GNUNET_new (struct SigningKey);
+  sk->donau_pub = *donau_pub;
+  sk->meta = *meta;
+  pid.public_key = donau_pub->eddsa_pub;
+  GNUNET_assert (
+    GNUNET_OK ==
+    GNUNET_CONTAINER_multipeermap_put (ksh->signkey_map,
+                                       &pid,
+                                       sk,
+                                       
GNUNET_CONTAINER_MULTIHASHMAPOPTION_UNIQUE_ONLY));
+}
 
-  /**
-   * What is the minimum key rotation frequency of
-   * valid donation unit keys?
-   */
-  struct GNUNET_TIME_Relative min_dk_frequency;
-};
 
 /**
  * Closure for #add_sign_key_cb.
@@ -480,6 +1296,7 @@ struct SignKeyCtx
   json_t *signkeys;
 };
 
+
 /**
  * Function called for all signing keys, used to build up the
  * respective JSON response.
@@ -498,29 +1315,91 @@ add_sign_key_cb (void *cls,
   struct SigningKey *sk = value;
 
   (void) pid;
-  // if (GNUNET_TIME_absolute_is_future (sk->meta.expire_sign.abs_time))
-  // {
+  //if (GNUNET_TIME_absolute_is_future (sk->meta.expire_sign.abs_time))
+  //{
   //  ctx->min_sk_frequency =
   //    GNUNET_TIME_relative_min (ctx->min_sk_frequency,
   //                              GNUNET_TIME_absolute_get_difference (
   //                                sk->meta.start.abs_time,
   //                                sk->meta.expire_sign.abs_time));
-  // }
-  GNUNET_assert (
-    0 ==
-    json_array_append_new (
-      ctx->signkeys,
-      GNUNET_JSON_PACK (
-        // GNUNET_JSON_pack_timestamp ("stamp_start",
-        //                            sk->meta.start),
-        // GNUNET_JSON_pack_timestamp ("stamp_expire",
-        //                            sk->meta.expire_sign),
-        // GNUNET_JSON_pack_timestamp ("stamp_end",
-        //                            sk->meta.expire_legal),
-        // GNUNET_JSON_pack_data_auto ("master_sig",
-        //                            &sk->master_sig),
-        GNUNET_JSON_pack_data_auto ("key",
-                                    &sk->donau_pub))));
+  //}
+  //GNUNET_assert (
+  //  0 ==
+  //  json_array_append_new (
+  //    ctx->signkeys,
+  //    GNUNET_JSON_PACK (
+  //      GNUNET_JSON_pack_timestamp ("stamp_start",
+  //                                  sk->meta.start),
+  //      GNUNET_JSON_pack_timestamp ("stamp_expire",
+  //                                  sk->meta.expire_sign),
+  //      GNUNET_JSON_pack_timestamp ("stamp_end",
+  //                                  sk->meta.expire_legal),
+  //      GNUNET_JSON_pack_data_auto ("key",
+  //                                  &sk->donau_pub))));
+  return GNUNET_OK;
+}
+
+
+/**
+ * Closure for #add_donation_unit_key_cb.
+ */
+struct DenomKeyCtx
+{
+  /**
+   * Heap for sorting active donation_unit keys by start time.
+   */
+  struct GNUNET_CONTAINER_Heap *heap;
+
+  /**
+   * What is the minimum key rotation frequency of
+   * valid donation_unit keys?
+   */
+  struct GNUNET_TIME_Relative min_dk_frequency;
+};
+
+
+/**
+ * Function called for all donation_unit keys, used to build up the
+ * JSON list of *revoked* donation_unit keys and the
+ * heap of non-revoked donation_unit keys by timeout.
+ *
+ * @param cls a `struct DenomKeyCtx`
+ * @param h_donation_unit_pub hash of the donation_unit key
+ * @param value a `struct DH_DonationUnitKey`
+ * @return #GNUNET_OK (continue to iterate)
+ */
+static enum GNUNET_GenericReturnValue
+add_donation_unit_key_cb (void *cls,
+                  const struct GNUNET_HashCode *h_donation_unit_pub,
+                  void *value)
+{
+  struct DenomKeyCtx *dkc = cls;
+  struct DH_DonationUnitKey *dk = value;
+
+  //if (dk->recoup_possible)
+  //{
+  //  GNUNET_assert (
+  //    0 ==
+  //    json_array_append_new (
+  //      dkc->recoup,
+  //      GNUNET_JSON_PACK (
+  //        GNUNET_JSON_pack_data_auto ("h_donation_unit_pub",
+  //                                    h_donation_unit_pub))));
+  //}
+  //else
+  //{
+  //  if (GNUNET_TIME_absolute_is_future (dk->meta.start.abs_time))
+  //  {
+  //    dkc->min_dk_frequency =
+  //      GNUNET_TIME_relative_min (dkc->min_dk_frequency,
+  //                                GNUNET_TIME_absolute_get_difference (
+  //                                  dk->meta.start.abs_time,
+  //                                  dk->meta.expire_withdraw.abs_time));
+  //  }
+  //  (void) GNUNET_CONTAINER_heap_insert (dkc->heap,
+  //                                       dk,
+  //                                       
dk->meta.start.abs_time.abs_value_us);
+  //}
   return GNUNET_OK;
 }
 
@@ -549,6 +1428,7 @@ setup_general_response_headers (void *cls,
                 MHD_add_response_header (response,
                                          MHD_HTTP_HEADER_LAST_MODIFIED,
                                          dat));
+
   /* Set cache control headers: our response varies depending on these headers 
*/
   GNUNET_break (MHD_YES ==
                 MHD_add_response_header (response,
@@ -563,311 +1443,379 @@ setup_general_response_headers (void *cls,
 
 
 /**
- * Update the "/keys" responses in @a ksh, computing the detailed replies.
- *
- * This function is to recompute all (including cherry-picked) responses we
- * might want to return, based on the state already in @a ksh.
- *
- * @param[in,out] ksh state handle to update
- * @return #GNUNET_OK on success
+ * Element in the `struct SignatureContext` array.
  */
-static enum GNUNET_GenericReturnValue
-finish_keys_response (struct DH_KeyStateHandle *ksh)
+struct SignatureElement
 {
-  enum GNUNET_GenericReturnValue ret = GNUNET_SYSERR;
-  json_t *recoup;
-  struct SignKeyCtx sctx;
-  json_t *grouped_donation_units = NULL;
-  struct GNUNET_TIME_Timestamp last_cherry_pick_date;
-  struct GNUNET_CONTAINER_Heap *heap;
-  struct GNUNET_HashContext *hash_context = NULL;
-  // struct GNUNET_HashCode grouped_hash_xor = {0};
-
-  sctx.signkeys = json_array ();
-  GNUNET_assert (NULL != sctx.signkeys);
-  sctx.min_sk_frequency = GNUNET_TIME_UNIT_FOREVER_REL;
-  GNUNET_CONTAINER_multipeermap_iterate (ksh->signkey_map,
-                                         &add_sign_key_cb,
-                                         &sctx);
-  recoup = json_array ();
-  GNUNET_assert (NULL != recoup);
-  heap = GNUNET_CONTAINER_heap_create (GNUNET_CONTAINER_HEAP_ORDER_MAX);
-  {
-    // struct DonationUnitKeyCtx dkc = {
-    // .heap = heap,
-    // .min_dk_frequency = GNUNET_TIME_UNIT_FOREVER_REL,
-    // };
-
-    // GNUNET_CONTAINER_multihashmap_iterate (ksh->denomkey_map,
-    //                                       &add_denom_key_cb,
-    //                                       &dkc);
-    // ksh->rekey_frequency
-    //  = GNUNET_TIME_relative_min (dkc.min_dk_frequency,
-    //                              sctx.min_sk_frequency);
-  }
 
-  hash_context = GNUNET_CRYPTO_hash_context_start ();
-
-  grouped_donation_units = json_array ();
-  GNUNET_assert (NULL != grouped_donation_units);
+  /**
+   * Offset of the donation_unit in the group array,
+   * for sorting (2nd rank, ascending).
+   */
+  unsigned int offset;
 
-  last_cherry_pick_date = GNUNET_TIME_UNIT_ZERO_TS;
+  /**
+   * Offset of the group in the donation_units array,
+   * for sorting (2nd rank, ascending).
+   */
+  unsigned int group_offset;
 
-  GNUNET_CONTAINER_heap_destroy (heap);
-  if (! GNUNET_TIME_absolute_is_zero (last_cherry_pick_date.abs_time))
-  {
-    struct GNUNET_HashCode hc;
+};
 
-    GNUNET_CRYPTO_hash_context_finish (hash_context,
-                                       &hc);
-    // if (GNUNET_OK !=
-    //    create_krd (ksh,
-    //                &hc,
-    //                last_cherry_pick_date,
-    //                sctx.signkeys,
-    //                recoup,
-    //                grouped_denominations,
-    //                &grouped_hash_xor))
-    // {
-    //  GNUNET_log (GNUNET_ERROR_TYPE_WARNING,
-    //              "Failed to generate key response data for %s\n",
-    //              GNUNET_TIME_timestamp2s (last_cherry_pick_date));
-    //  goto CLEANUP;
-    // }
-    ksh->management_only = false;
-  }
-  else
-  {
-    GNUNET_log (GNUNET_ERROR_TYPE_WARNING,
-                "No donation unit keys available. Refusing to generate /keys 
response.\n");
-    GNUNET_CRYPTO_hash_context_abort (hash_context);
-  }
+/**
+ * Context for collecting the array of master signatures
+ * needed to verify the donau_sig online signature.
+ */
+struct SignatureContext
+{
+  /**
+   * Array of signatures to hash over.
+   */
+  struct SignatureElement *elements;
 
-  ret = GNUNET_OK;
+  /**
+   * Write offset in the @e elements array.
+   */
+  unsigned int elements_pos;
 
-// CLEANUP:
-  json_decref (grouped_donation_units);
-  json_decref (sctx.signkeys);
-  json_decref (recoup);
-  return ret;
-}
+  /**
+   * Allocated space for @e elements.
+   */
+  unsigned int elements_size;
+};
 
 
 /**
- * Free donation unit key data.
+ * Determine order to sort two elements by before
+ * we hash the master signatures.  Used for
+ * sorting with qsort().
  *
- * @param cls a `struct DH_KeyStateHandle`, unused
- * @param h_donation_unit_pub hash of the donation unit public key, unused
- * @param value a `struct DH_DonationUnitKey` to free
- * @return #GNUNET_OK (continue to iterate)
+ * @param a pointer to a `struct SignatureElement`
+ * @param b pointer to a `struct SignatureElement`
+ * @return 0 if equal, -1 if a < b, 1 if a > b.
  */
-static enum GNUNET_GenericReturnValue
-clear_donation_unit_cb (void *cls,
-                        const struct GNUNET_HashCode *h_donation_unit_pub,
-                        void *value)
+static int
+signature_context_sort_cb (const void *a,
+                           const void *b)
 {
-  struct DH_DonationUnitKey *dk = value;
+  const struct SignatureElement *sa = a;
+  const struct SignatureElement *sb = b;
 
-  (void) cls;
-  (void) h_donation_unit_pub;
-  // TALER_denom_pub_free (&dk->denom_pub);
-  GNUNET_free (dk);
-  return GNUNET_OK;
+  if (sa->group_offset < sb->group_offset)
+    return -1;
+  if (sa->group_offset > sb->group_offset)
+    return 1;
+  if (sa->offset < sb->offset)
+    return -1;
+  if (sa->offset > sb->offset)
+    return 1;
+  /* We should never have two disjoint elements
+     with same time and offset */
+  GNUNET_assert (sa == sb);
+  return 0;
 }
 
 
 /**
- * Free donation unit key data.
- *
- * @param cls a `struct DH_KeyStateHandle`, unused
- * @param pid the online signing key (type-disguised), unused
- * @param value a `struct SigningKey` to free
- * @return #GNUNET_OK (continue to iterate)
- */
-static enum GNUNET_GenericReturnValue
-clear_signkey_cb (void *cls,
-                  const struct GNUNET_PeerIdentity *pid,
-                  void *value)
+ *GroupData is the value we store for each group meta-data */
+struct GroupData
 {
-  struct SigningKey *sk = value;
+  /**
+   * The json blob with the group meta-data and list of donation_units
+   */
+  json_t *json;
 
-  (void) cls;
-  (void) pid;
-  GNUNET_free (sk);
-  return GNUNET_OK;
-}
+  /**
+   * List of donation_units for the group,
+   * included in @e json, do not free separately!
+   */
+  json_t *list;
+
+  /**
+   * Offset of the group in the final array.
+   */
+  unsigned int group_off;
+
+};
 
 
 /**
- * Clear memory for responses to "/keys" in @a ksh.
+ * Helper function called to clean up the group data
+ * in the donation_units_by_group below.
  *
- * @param[in,out] ksh key state to update
+ * @param cls unused
+ * @param key unused
+ * @param value a `struct GroupData` to free
+ * @return #GNUNET_OK
  */
-static void
-clear_response_cache (struct DH_KeyStateHandle *ksh)
+static int
+free_group (void *cls,
+            const struct GNUNET_HashCode *key,
+            void *value)
 {
-  for (unsigned int i = 0; i<ksh->krd_array_length; i++)
-  {
-    struct KeysResponseData *krd = &ksh->krd_array[i];
+  struct GroupData *gd = value;
 
-    MHD_destroy_response (krd->response_compressed);
-    MHD_destroy_response (krd->response_uncompressed);
-    GNUNET_free (krd->etag);
-  }
-  GNUNET_array_grow (ksh->krd_array,
-                     ksh->krd_array_length,
-                     0);
+  (void) cls;
+  (void) key;
+  GNUNET_free (gd);
+  return GNUNET_OK;
 }
 
 
 /**
- * Synchronize helper state. Polls the key helper for updates.
+ * Update the "/keys" responses in @a ksh, computing the detailed replies.
  *
- * @param[in,out] hs helper state to synchronize
+ * This function is to recompute all (including cherry-picked) responses we
+ * might want to return, based on the state already in @a ksh.
+ *
+ * @param[in,out] ksh state handle to update
+ * @return #GNUNET_OK on success
  */
-static void
-sync_key_helpers (struct HelperState *hs)
+static enum GNUNET_GenericReturnValue
+finish_keys_response (struct DH_KeyStateHandle *ksh)
 {
-  TALER_CRYPTO_helper_rsa_poll (hs->rsadh);
-  TALER_CRYPTO_helper_cs_poll (hs->csdh);
-  TALER_CRYPTO_helper_esign_poll (hs->esh);
-}
+  enum GNUNET_GenericReturnValue ret = GNUNET_SYSERR;
+  struct SignKeyCtx sctx = {
+    .min_sk_frequency = GNUNET_TIME_UNIT_FOREVER_REL
+  };
+  json_t *grouped_donation_units = NULL;
+  struct GNUNET_TIME_Timestamp last_cherry_pick_date;
+  struct GNUNET_CONTAINER_Heap *heap;
+  struct SignatureContext sig_ctx = { 0 };
 
+  sctx.signkeys = json_array ();
+  GNUNET_assert (NULL != sctx.signkeys);
+  grouped_donation_units = json_array ();
+  GNUNET_assert (NULL != grouped_donation_units);
 
-/**
- * Destroy helper state. Does NOT call free() on @a hs, as that
- * state is not separately allocated!  Dual to #setup_key_helpers().
- *
- * @param[in] hs helper state to free, but NOT the @a hs pointer itself!
- */
-static void
-destroy_key_helpers (struct HelperState *hs)
-{
-  // GNUNET_CONTAINER_multihashmap_iterate (hs->denom_keys,
-  //                                       &free_denom_cb,
-  //                                       hs);
-  // GNUNET_CONTAINER_multihashmap_destroy (hs->rsa_keys);
-  // hs->rsa_keys = NULL;
-  // GNUNET_CONTAINER_multihashmap_destroy (hs->cs_keys);
-  // hs->cs_keys = NULL;
-  // GNUNET_CONTAINER_multihashmap_destroy (hs->denom_keys);
-  // hs->denom_keys = NULL;
-  // GNUNET_CONTAINER_multipeermap_iterate (hs->esign_keys,
-  //                                       &free_esign_cb,
-  //                                       hs);
-  // GNUNET_CONTAINER_multipeermap_destroy (hs->esign_keys);
-  hs->esign_keys = NULL;
-  if (NULL != hs->rsadh)
-  {
-    TALER_CRYPTO_helper_rsa_disconnect (hs->rsadh);
-    hs->rsadh = NULL;
-  }
-  if (NULL != hs->csdh)
+  GNUNET_CONTAINER_multipeermap_iterate (ksh->signkey_map,
+                                         &add_sign_key_cb,
+                                         &sctx);
+  if (0 == json_array_size (sctx.signkeys))
   {
-    TALER_CRYPTO_helper_cs_disconnect (hs->csdh);
-    hs->csdh = NULL;
+    GNUNET_log (GNUNET_ERROR_TYPE_WARNING,
+                "No online signing keys available. Refusing to generate /keys 
response.\n");
+    ret = GNUNET_NO;
+    goto CLEANUP;
   }
-  if (NULL != hs->esh)
+  heap = GNUNET_CONTAINER_heap_create (GNUNET_CONTAINER_HEAP_ORDER_MAX);
   {
-    TALER_CRYPTO_helper_esign_disconnect (hs->esh);
-    hs->esh = NULL;
+    struct DenomKeyCtx dkc = {
+      .heap = heap,
+      .min_dk_frequency = GNUNET_TIME_UNIT_FOREVER_REL,
+    };
+
+    GNUNET_CONTAINER_multihashmap_iterate (ksh->donation_unitkey_map,
+                                           &add_donation_unit_key_cb,
+                                           &dkc);
+    ksh->rekey_frequency
+      = GNUNET_TIME_relative_min (dkc.min_dk_frequency,
+                                  sctx.min_sk_frequency);
   }
-}
 
+  last_cherry_pick_date = GNUNET_TIME_UNIT_ZERO_TS;
+
+  {
+    struct DH_DonationUnitKey *dk;
+    struct GNUNET_CONTAINER_MultiHashMap *donation_units_by_group;
+
+    donation_units_by_group =
+      GNUNET_CONTAINER_multihashmap_create (1024,
+                                            GNUNET_NO /* NO, because keys are 
only on the stack */);
+    /* heap = max heap, sorted by start time */
+    while (NULL != (dk = GNUNET_CONTAINER_heap_remove_root (heap)))
+    {
+      //if (GNUNET_TIME_timestamp_cmp (last_cherry_pick_date,
+      //                               !=,
+      //                               dk->meta.start) &&
+      //    (! GNUNET_TIME_absolute_is_zero (last_cherry_pick_date.abs_time)) )
+      //{
+      //  /*
+      //   * This is not the first entry in the heap (because 
last_cherry_pick_date !=
+      //   * GNUNET_TIME_UNIT_ZERO_TS) and the previous entry had a different
+      //   * start time.  Therefore, we create a new entry in ksh.
+      //   */
+      //  struct GNUNET_HashCode hc;
+//
+      //  if (GNUNET_OK !=
+      //      create_krd (ksh,
+      //                  &hc,
+      //                  last_cherry_pick_date,
+      //                  sctx.signkeys,
+      //                  recoup,
+      //                  grouped_donation_units))
+      //  {
+      //    GNUNET_log (GNUNET_ERROR_TYPE_WARNING,
+      //                "Failed to generate key response data for %s\n",
+      //                GNUNET_TIME_timestamp2s (last_cherry_pick_date));
+      //    /* drain heap before destroying it */
+      //    while (NULL != (dk = GNUNET_CONTAINER_heap_remove_root (heap)))
+      //      /* intentionally empty */;
+      //    GNUNET_CONTAINER_heap_destroy (heap);
+      //    goto CLEANUP;
+      //  }
+      //}
+
+      //last_cherry_pick_date = dk->meta.start;
+      /*
+       * Group the donation_units by {cipher, value, fees, age_mask}.
+       *
+       * For each group we save the group meta-data and the list of
+       * donation_units in this group as a json-blob in the multihashmap
+       * donation_units_by_group.
+       */
+      {
+        struct GroupData *group;
+        json_t *entry;
+        struct GNUNET_HashCode key;
+        struct DONAU_DonationUnitGroup meta = {
+          .cipher = dk->donation_unit_pub.bsign_pub_key->cipher,
+        //  .value = dk->meta.value,
+        };
+
+        /* Search the group/JSON-blob for the key */
+        //DONAU_donation_unit_group_get_key (&meta,
+        //                                  &key);
+        group = GNUNET_CONTAINER_multihashmap_get (
+          donation_units_by_group,
+          &key);
+        if (NULL == group)
+        {
+          /* There is no group for this meta-data yet, so we create a new 
group */
+          const char *cipher;
+
+          group = GNUNET_new (struct GroupData);
+
+          /* Create a new array for the donation_units in this group */
+          group->list = json_array ();
+          GNUNET_assert (NULL != group->list);
+          group->json = GNUNET_JSON_PACK (
+            GNUNET_JSON_pack_string ("cipher",
+                                     cipher),
+            GNUNET_JSON_pack_array_steal ("donation_units",
+                                          group->list));
+            //DONAU_JSON_pack_amount ("value",
+            //                        &meta.value));
+          GNUNET_assert (NULL != group->json);
+
+          group->group_off
+            = json_array_size (grouped_donation_units);
+          GNUNET_assert (0 ==
+                         json_array_append_new (
+                           grouped_donation_units,
+                           group->json));
+          GNUNET_assert (
+            GNUNET_OK ==
+            GNUNET_CONTAINER_multihashmap_put (donation_units_by_group,
+                                               &key,
+                                               group,
+                                               
GNUNET_CONTAINER_MULTIHASHMAPOPTION_UNIQUE_ONLY));
+        }
+
+        /* Now that we have found/created the right group, add the
+           donation_unit to the list */
+        {
+          struct HelperDonationUnit *hd;
+          struct GNUNET_JSON_PackSpec key_spec;
+          bool private_key_lost;
+
+          hd = GNUNET_CONTAINER_multihashmap_get 
(ksh->helpers->donation_unit_keys,
+                                                  
&dk->h_donation_unit_pub.hash);
+          private_key_lost
+            = (NULL == hd) ||
+              GNUNET_TIME_absolute_is_past (
+                GNUNET_TIME_absolute_add (
+                  hd->start_time.abs_time,
+                  hd->validity_duration));
+          //switch (meta.cipher)
+          //{
+          //case GNUNET_CRYPTO_BSA_RSA:
+          //  key_spec =
+          //    GNUNET_JSON_pack_rsa_public_key (
+          //      "rsa_pub",
+          //      dk->donation_unit_pub.bsign_pub_key->details.rsa_public_key);
+          //  break;
+          //case GNUNET_CRYPTO_BSA_CS:
+          //  key_spec =
+          //    GNUNET_JSON_pack_data_varsize (
+          //      "cs_pub",
+          //      &dk->donation_unit_pub.bsign_pub_key->details.cs_public_key,
+          //      sizeof 
(dk->donation_unit_pub.bsign_pub_key->details.cs_public_key));
+          //  break;
+          //default:
+          //  GNUNET_assert (false);
+          //}
+
+          entry = GNUNET_JSON_PACK (
+            GNUNET_JSON_pack_allow_null (
+              private_key_lost
+              ? GNUNET_JSON_pack_bool ("lost",
+                                       true)
+              : GNUNET_JSON_pack_string ("dummy",
+                                         NULL)),
+            //GNUNET_JSON_pack_timestamp ("stamp_start",
+            //                            dk->meta.start),
+            //GNUNET_JSON_pack_timestamp ("stamp_expire_withdraw",
+            //                            dk->meta.expire_withdraw),
+            //GNUNET_JSON_pack_timestamp ("stamp_expire_deposit",
+            //                            dk->meta.expire_deposit),
+            //GNUNET_JSON_pack_timestamp ("stamp_expire_legal",
+            //                            dk->meta.expire_legal),
+            key_spec
+            );
+          GNUNET_assert (NULL != entry);
+        }
+
+        /* Finally, add the donation_unit to the list of donation_units in this
+           group */
+        GNUNET_assert (json_is_array (group->list));
+        GNUNET_assert (0 ==
+                       json_array_append_new (group->list,
+                                              entry));
+      }
+    } /* loop over heap ends */
 
-/**
- * Free resources associated with @a cls, possibly excluding
- * the helper data.
- *
- * @param[in] ksh key state to release
- * @param free_helper true to also release the helper state
- */
-static void
-destroy_key_state (struct DH_KeyStateHandle *ksh,
-                   bool free_helper)
-{
-  // struct DH_GlobalFee *gf;
+    GNUNET_CONTAINER_multihashmap_iterate (donation_units_by_group,
+                                           &free_group,
+                                           NULL);
+    GNUNET_CONTAINER_multihashmap_destroy (donation_units_by_group);
+  }
+  GNUNET_CONTAINER_heap_destroy (heap);
 
-  clear_response_cache (ksh);
-  // while (NULL != (gf = ksh->gf_head))
-  // {
-  //  GNUNET_CONTAINER_DLL_remove (ksh->gf_head,
-  //                               ksh->gf_tail,
-  //                               gf);
-  //  GNUNET_free (gf);
-  // }
-  GNUNET_CONTAINER_multihashmap_iterate (ksh->denomkey_map,
-                                         &clear_donation_unit_cb,
-                                         ksh);
-  GNUNET_CONTAINER_multihashmap_destroy (ksh->denomkey_map);
-  GNUNET_CONTAINER_multipeermap_iterate (ksh->signkey_map,
-                                         &clear_signkey_cb,
-                                         ksh);
-  GNUNET_CONTAINER_multipeermap_destroy (ksh->signkey_map);
-  // json_decref (ksh->auditors);
-  // ksh->auditors = NULL;
-  // json_decref (ksh->global_fees);
-  // ksh->global_fees = NULL;
-  if (free_helper)
+  if (! GNUNET_TIME_absolute_is_zero (last_cherry_pick_date.abs_time))
   {
-    destroy_key_helpers (ksh->helpers);
-    GNUNET_free (ksh->helpers);
+    struct GNUNET_HashCode hc;
+
+    //if (GNUNET_OK !=
+    //    create_krd (ksh,
+    //                &hc,
+    //                last_cherry_pick_date,
+    //                sctx.signkeys,
+    //                grouped_donation_units))
+    //{
+    //  GNUNET_log (GNUNET_ERROR_TYPE_WARNING,
+    //              "Failed to generate key response data for %s\n",
+    //              GNUNET_TIME_timestamp2s (last_cherry_pick_date));
+    //  goto CLEANUP;
+    //}
+    ksh->management_only = false;
+
   }
-  if (NULL != ksh->management_keys_reply)
+  else
   {
-    json_decref (ksh->management_keys_reply);
-    ksh->management_keys_reply = NULL;
+    GNUNET_log (GNUNET_ERROR_TYPE_WARNING,
+                "No donation_unit keys available. Refusing to generate /keys 
response.\n");
   }
-  GNUNET_free (ksh);
-}
-
+  ret = GNUNET_OK;
 
-/**
- * Setup helper state.
- *
- * @param[out] hs helper state to initialize
- * @return #GNUNET_OK on success
- */
-static enum GNUNET_GenericReturnValue
-setup_key_helpers (struct HelperState *hs)
-{
-  // hs->denom_keys
-  //  = GNUNET_CONTAINER_multihashmap_create (1024,
-  //                                          GNUNET_YES);
-  hs->rsa_keys
-    = GNUNET_CONTAINER_multihashmap_create (1024,
-                                            GNUNET_YES);
-  hs->cs_keys
-    = GNUNET_CONTAINER_multihashmap_create (1024,
-                                            GNUNET_YES);
-  hs->esign_keys
-    = GNUNET_CONTAINER_multipeermap_create (32,
-                                            GNUNET_NO /* MUST BE NO! */);
-  // hs->rsadh = TALER_CRYPTO_helper_rsa_connect (DH_cfg,
-  //                                             &helper_rsa_cb,
-  //                                             hs);
-  // if (NULL == hs->rsadh)
-  // {
-  //  destroy_key_helpers (hs);
-  //  return GNUNET_SYSERR;
-  // }
-  // hs->csdh = TALER_CRYPTO_helper_cs_connect (DH_cfg,
-  //                                           &helper_cs_cb,
-  //                                           hs);
-  // if (NULL == hs->csdh)
-  // {
-  //  destroy_key_helpers (hs);
-  //  return GNUNET_SYSERR;
-  // }
-  // hs->esh = TALER_CRYPTO_helper_esign_connect (DH_cfg,
-  //                                             &helper_esign_cb,
-  //                                             hs);
-  // if (NULL == hs->esh)
-  // {
-  //  destroy_key_helpers (hs);
-  //  return GNUNET_SYSERR;
-  // }
-  return GNUNET_OK;
+CLEANUP:
+  GNUNET_array_grow (sig_ctx.elements,
+                     sig_ctx.elements_size,
+                     0);
+  json_decref (grouped_donation_units);
+  if (NULL != sctx.signkeys)
+    json_decref (sctx.signkeys);
+  return ret;
 }
 
 
@@ -880,11 +1828,11 @@ setup_key_helpers (struct HelperState *hs)
  * @return NULL on error (i.e. failed to access database)
  */
 static struct DH_KeyStateHandle *
-build_key_state (struct HelperState *hs /*,
-                 bool management_only*/)
+build_key_state (struct HelperState *hs,
+                 bool management_only)
 {
   struct DH_KeyStateHandle *ksh;
-  // enum GNUNET_DB_QueryStatus qs;
+  enum GNUNET_DB_QueryStatus qs;
 
   ksh = GNUNET_new (struct DH_KeyStateHandle);
   ksh->signature_expires = GNUNET_TIME_UNIT_FOREVER_TS;
@@ -907,56 +1855,48 @@ build_key_state (struct HelperState *hs /*,
   {
     ksh->helpers = hs;
   }
-  ksh->denomkey_map = GNUNET_CONTAINER_multihashmap_create (1024,
+  ksh->donation_unitkey_map = GNUNET_CONTAINER_multihashmap_create (1024,
                                                             true);
   ksh->signkey_map = GNUNET_CONTAINER_multipeermap_create (32,
-                                                           false /* MUST be 
false! */
-                                                           );
+                                                           false /* MUST be 
false! */);
   /* NOTE: fetches master-signed signkeys, but ALSO those that were revoked! */
-  // GNUNET_break (GNUNET_OK ==
-  //              DH_plugin->preflight (DH_plugin->cls));
-  // if (qs < 0)
-  // {
+  GNUNET_break (GNUNET_OK ==
+                DH_plugin->preflight (DH_plugin->cls));
+  
+  //qs = DH_plugin->iterate_donation_units (DH_plugin->cls,
+  //                                        &donation_unit_info_cb,
+  //                                        ksh);
+  //if (qs < 0)
+  //{
   //  GNUNET_break (GNUNET_DB_STATUS_SOFT_ERROR != qs);
   //  GNUNET_break (GNUNET_DB_STATUS_HARD_ERROR != qs);
   //  destroy_key_state (ksh,
   //                     true);
   //  return NULL;
-  // }
-  // qs = DH_plugin->iterate_denominations (DH_plugin->cls,
-  //                                       &denomination_info_cb,
-  //                                       ksh);
-  // if (qs < 0)
-  // {
-  //  GNUNET_break (GNUNET_DB_STATUS_SOFT_ERROR != qs);
-  //  GNUNET_break (GNUNET_DB_STATUS_HARD_ERROR != qs);
-  //  destroy_key_state (ksh,
-  //                     true);
-  //  return NULL;
-  // }
-  /* NOTE: ONLY fetches non-revoked AND master-signed signkeys! */
-  // qs = DH_plugin->iterate_active_signkeys (DH_plugin->cls,
-  //                                         &signkey_info_cb,
-  //                                         ksh);
-  // if (qs < 0)
-  // {
+  //}
+  ///* NOTE: ONLY fetches non-revoked AND master-signed signkeys! */
+  //qs = DH_plugin->iterate_active_signkeys (DH_plugin->cls,
+  //                                          &signkey_info_cb,
+  //                                          ksh);
+  //if (qs < 0)
+  //{
   //  GNUNET_break (0);
   //  destroy_key_state (ksh,
   //                     true);
   //  return NULL;
-  // }
+  //}
 
-  // if (management_only)
-  // {
-  //   ksh->management_only = true;
-  //   return ksh;
-  // }
+  if (management_only)
+  {
+    ksh->management_only = true;
+    return ksh;
+  }
 
   if (GNUNET_OK !=
       finish_keys_response (ksh))
   {
     GNUNET_log (GNUNET_ERROR_TYPE_WARNING,
-                "Could not finish /keys response (likely no signing keys 
available yet)\n");
+                "Could not finish /keys response (required data not configured 
yet)\n");
     destroy_key_state (ksh,
                        true);
     return NULL;
@@ -971,28 +1911,29 @@ DH_keys_update_states ()
 {
   struct GNUNET_DB_EventHeaderP es = {
     .size = htons (sizeof (es)),
-    // .type = htons (TALER_DBEVENT_DONAU_KEYS_UPDATED),
+    .type = htons (TALER_DBEVENT_EXCHANGE_KEYS_UPDATED),
   };
 
   DH_plugin->event_notify (DH_plugin->cls,
-                           &es,
-                           NULL,
-                           0);
+                            &es,
+                            NULL,
+                            0);
   key_generation++;
-  // DH_resume_keys_requests (false);
+  DH_resume_keys_requests (false);
 }
 
 
 static struct DH_KeyStateHandle *
-DH_keys_get_state (/*bool management_only*/)
+keys_get_state (bool management_only)
 {
   struct DH_KeyStateHandle *old_ksh;
   struct DH_KeyStateHandle *ksh;
+
   old_ksh = key_state;
   if (NULL == old_ksh)
   {
-    ksh = build_key_state (NULL /*, management_only*/);
-    ksh = NULL;
+    ksh = build_key_state (NULL,
+                           management_only);
     if (NULL == ksh)
       return NULL;
     key_state = ksh;
@@ -1005,8 +1946,8 @@ DH_keys_get_state (/*bool management_only*/)
                 "Rebuilding /keys, generation upgrade from %llu to %llu\n",
                 (unsigned long long) old_ksh->key_generation,
                 (unsigned long long) key_generation);
-    ksh = build_key_state (old_ksh->helpers /*,
-                           management_only*/);
+    ksh = build_key_state (old_ksh->helpers,
+                           management_only);
     key_state = ksh;
     old_ksh->helpers = NULL;
     destroy_key_state (old_ksh,
@@ -1018,202 +1959,404 @@ DH_keys_get_state (/*bool management_only*/)
 }
 
 
-/**
- * Closure for #add_future_donation_unit_cb and #add_future_signkey_cb.
- */
-struct FutureBuilderContext
+struct DH_KeyStateHandle *
+DH_keys_get_state_for_management_only (void)
+{
+  return keys_get_state (true);
+}
+
+
+struct DH_KeyStateHandle *
+DH_keys_get_state (void)
 {
-  /**
-   * Our key state.
-   */
   struct DH_KeyStateHandle *ksh;
 
-  /**
-   * Array of donation unit keys.
-   */
-  json_t *donation_units;
+  ksh = keys_get_state (false);
+  if (NULL == ksh)
+    return NULL;
 
-  /**
-   * Array of signing keys.
-   */
-  json_t *signkeys;
+  if (ksh->management_only)
+  {
+    if (GNUNET_OK !=
+        finish_keys_response (ksh))
+      return NULL;
+  }
+
+  return ksh;
+}
+
+
+struct DH_DonationUnitKey *
+DH_keys_donation_unit_by_hash (
+  const struct DONAU_DonationUnitHashP *h_donation_unit_pub,
+  struct MHD_Connection *conn,
+  MHD_RESULT *mret)
+{
+  struct DH_KeyStateHandle *ksh;
+
+  ksh = DH_keys_get_state ();
+  if (NULL == ksh)
+  {
+    *mret = TALER_MHD_reply_with_error (conn,
+                                        MHD_HTTP_INTERNAL_SERVER_ERROR,
+                                        TALER_EC_EXCHANGE_GENERIC_KEYS_MISSING,
+                                        NULL);
+    return NULL;
+  }
+
+  return DH_keys_donation_unit_by_hash_from_state (ksh,
+                                                   h_donation_unit_pub,
+                                                   conn,
+                                                   mret);
+}
+
+
+struct DH_DonationUnitKey *
+DH_keys_donation_unit_by_hash_from_state (
+  const struct DH_KeyStateHandle *ksh,
+  const struct DONAU_DonationUnitHashP *h_donation_unit_pub,
+  struct MHD_Connection *conn,
+  MHD_RESULT *mret)
+{
+  struct DH_DonationUnitKey *dk;
+
+  dk = GNUNET_CONTAINER_multihashmap_get (ksh->donation_unitkey_map,
+                                          &h_donation_unit_pub->hash);
+  if (NULL == dk)
+  {
+    if (NULL == conn)
+      return NULL;
+    //*mret = DH_RESPONSE_reply_unknown_donation_unit_pub_hash (conn,
+    //                                                   h_donation_unit_pub);
+    //return NULL;
+  }
+  return dk;
+}
+
+
+enum TALER_ErrorCode
+DH_keys_donation_unit_batch_sign (
+  unsigned int csds_length,
+  const struct DH_CoinSignData csds[static csds_length],
+  struct DONAU_BlindedDonationUnitSignature bss[static csds_length])
+{
+  struct DH_KeyStateHandle *ksh;
+  struct HelperDonationUnit *hd;
+  struct TALER_CRYPTO_RsaSignRequest rsrs[csds_length];
+  struct TALER_CRYPTO_CsSignRequest csrs[csds_length];
+  struct DONAU_BlindedDonationUnitSignature rs[csds_length];
+  struct DONAU_BlindedDonationUnitSignature cs[csds_length];
+  unsigned int rsrs_pos = 0;
+  unsigned int csrs_pos = 0;
+  enum TALER_ErrorCode ec;
+
+  ksh = DH_keys_get_state ();
+  if (NULL == ksh)
+    return TALER_EC_EXCHANGE_GENERIC_KEYS_MISSING;
+  for (unsigned int i = 0; i<csds_length; i++)
+  {
+    const struct DONAU_DonationUnitHashP *h_donation_unit_pub = 
csds[i].h_donation_unit_pub;
+    const struct DONAU_BlindedDonationUnit *bp = csds[i].bp;
+
+    hd = GNUNET_CONTAINER_multihashmap_get (ksh->helpers->donation_unit_keys,
+                                            &h_donation_unit_pub->hash);
+    if (NULL == hd)
+      return TALER_EC_EXCHANGE_GENERIC_DENOMINATION_KEY_UNKNOWN;
+    //if (bp->blinded_message->cipher !=
+    //    hd->donation_unit_pub.bsign_pub_key->cipher)
+    //  return TALER_EC_GENERIC_INTERNAL_INVARIANT_FAILURE;
+    //switch (hd->donation_unit_pub.bsign_pub_key->cipher)
+    //{
+    //case GNUNET_CRYPTO_BSA_RSA:
+    //  rsrs[rsrs_pos].h_rsa = &hd->h_details.h_rsa;
+    //  rsrs[rsrs_pos].msg
+    //    = bp->blinded_message->details.rsa_blinded_message.blinded_msg;
+    //  rsrs[rsrs_pos].msg_size
+    //    = bp->blinded_message->details.rsa_blinded_message.blinded_msg_size;
+    //  rsrs_pos++;
+    //  break;
+    //case GNUNET_CRYPTO_BSA_CS:
+    //  csrs[csrs_pos].h_cs = &hd->h_details.h_cs;
+    //  csrs[csrs_pos].blinded_donation_unit
+    //    = &bp->blinded_message->details.cs_blinded_message;
+    //  csrs_pos++;
+    //  break;
+    //default:
+    //  return TALER_EC_GENERIC_INTERNAL_INVARIANT_FAILURE;
+    //}
+  }
+
+  if ( (0 != csrs_pos) &&
+       (0 != rsrs_pos) )
+  {
+    memset (rs,
+            0,
+            sizeof (rs));
+    memset (cs,
+            0,
+            sizeof (cs));
+  }
+  ec = TALER_EC_NONE;
+  //if (0 != csrs_pos)
+  //{
+  //  ec = TALER_CRYPTO_helper_cs_batch_sign (
+  //    ksh->helpers->csdh,
+  //    csrs_pos,
+  //    csrs,
+  //    (0 == rsrs_pos) ? bss : cs);
+  //  if (TALER_EC_NONE != ec)
+  //  {
+  //    for (unsigned int i = 0; i<csrs_pos; i++)
+  //      DONAU_blinded_donation_unit_sig_free (&cs[i]);
+  //    return ec;
+  //  }
+  //}
+  if (0 != rsrs_pos)
+  {
+    ec = TALER_CRYPTO_helper_rsa_batch_sign (
+      ksh->helpers->rsadh,
+      rsrs_pos,
+      rsrs,
+      (0 == csrs_pos) ? bss : rs);
+    if (TALER_EC_NONE != ec)
+    {
+      for (unsigned int i = 0; i<csrs_pos; i++)
+        DONAU_blinded_donation_unit_sig_free (&cs[i]);
+      for (unsigned int i = 0; i<rsrs_pos; i++)
+        DONAU_blinded_donation_unit_sig_free (&rs[i]);
+      return ec;
+    }
+  }
+
+  if ( (0 != csrs_pos) &&
+       (0 != rsrs_pos) )
+  {
+    rsrs_pos = 0;
+    csrs_pos = 0;
+    for (unsigned int i = 0; i<csds_length; i++)
+    {
+      const struct DONAU_BlindedDonationUnit *bp = csds[i].bp;
+
+      //switch (bp->blinded_message->cipher)
+      //{
+      //case GNUNET_CRYPTO_BSA_RSA:
+      //  bss[i] = rs[rsrs_pos++];
+      //  break;
+      //case GNUNET_CRYPTO_BSA_CS:
+      //  bss[i] = cs[csrs_pos++];
+      //  break;
+      //default:
+      //  GNUNET_assert (0);
+      //}
+    }
+  }
+  return TALER_EC_NONE;
+}
 
-};
 
-// /**
-//  * Function called on all of our current and future donation unit keys
-//  * known to the helper process. Filters out those that are current
-//  * and adds the remaining donation unit keys (with their configuration
-//  * data) to the JSON array.
-//  *
-//  * @param cls the `struct FutureBuilderContext *`
-//  * @param h_donation_unit_pub hash of the donation unit public key
-//  * @param value a `struct HelperDenomination`
-//  * @return #GNUNET_OK (continue to iterate)
-//  */
-// static enum GNUNET_GenericReturnValue
-// add_donation_unitkey_cb (void *cls,
-//                          const struct GNUNET_HashCode *h_donation_unit_pub,
-//                          void *value)
-// {
-//   struct FutureBuilderContext *fbc = cls;
-//   struct HelperDonationUnit *helper_donation_unit = value;
-//   struct DH_DonationUnitKey *donation_unit_key;
-//   struct DONAUDB_DonationUnitKeyMetaData meta = {0};
-
-//   donation_unit_key = GNUNET_CONTAINER_multihashmap_get 
(fbc->ksh->denomkey_map,
-//                                                          
h_donation_unit_pub);
-//   if (NULL != donation_unit_key)
-//     return GNUNET_OK; /* skip: this key is already active! */
-//   // if (GNUNET_TIME_relative_is_zero (hd->validity_duration))
-//   // return GNUNET_OK; /* this key already expired! */
-
-//   GNUNET_assert (
-//     0 ==
-//     json_array_append_new (
-//       fbc->donation_units,
-//       GNUNET_JSON_PACK (
-//         TALER_JSON_pack_amount ("value",
-//                                 &meta.value),
-//         GNUNET_JSON_pack_uint64 ("year",
-//                                  meta.validity_year),
-//         GNUNET_JSON_pack_data_auto ("donation_unit_pub",
-//                                     
&helper_donation_unit->donation_unit_pub)
-//         // GNUNET_JSON_pack_string ("section_name",
-//         //  helper_donation_unit->section_name)
-//         )));
-//   return GNUNET_OK;
-// }
-
-
-// /**
-//  * Function called on all of our current and future exchange signing keys
-//  * known to the helper process. Filters out those that are current
-//  * and adds the remaining signing keys (with their configuration
-//  * data) to the JSON array.
-//  *
-//  * @param cls the `struct FutureBuilderContext *`
-//  * @param pid actually the exchange public key (type disguised)
-//  * @param value a `struct HelperDenomination`
-//  * @return #GNUNET_OK (continue to iterate)
-//  */
-// static enum GNUNET_GenericReturnValue
-// add_signkey_cb (void *cls,
-//                 const struct GNUNET_PeerIdentity *pid,
-//                 void *value)
-// {
-//   struct FutureBuilderContext *fbc = cls;
-//   struct HelperSignkey *hsk = value;
-//   struct SigningKey *sk;
-//   // struct GNUNET_TIME_Timestamp stamp_expire;
-//   // struct GNUNET_TIME_Timestamp legal_end;
-
-//   sk = GNUNET_CONTAINER_multipeermap_get (fbc->ksh->signkey_map,
-//                                           pid);
-//   if (NULL != sk)
-//     return GNUNET_OK; /* skip: this key is already active */
-//   // if (GNUNET_TIME_relative_is_zero (hsk->validity_duration))
-//   // return GNUNET_OK; /* this key already expired! */
-//   // stamp_expire = GNUNET_TIME_absolute_to_timestamp (
-//   // GNUNET_TIME_absolute_add (hsk->start_time.abs_time,
-//   // hsk->validity_duration));
-//   // legal_end = GNUNET_TIME_absolute_to_timestamp (
-//   // GNUNET_TIME_absolute_add (stamp_expire.abs_time,
-//   // signkey_legal_duration));
-//   GNUNET_assert (0 ==
-//                  json_array_append_new (
-//                    fbc->signkeys,
-//                    GNUNET_JSON_PACK (
-//                      GNUNET_JSON_pack_data_auto ("key",
-//                                                  &hsk->donau_pub),
-//                      //  GNUNET_JSON_pack_timestamp ("stamp_end",
-//                      //  legal_end),
-//                      GNUNET_JSON_pack_data_auto ("year",
-//                                                  &hsk->year)
-//                      //  GNUNET_JSON_pack_data_auto ("signkey_secmod_sig",
-//                      //  &hsk->sm_sig)
-//                      )));
-//   return GNUNET_OK;
-// }
-
-
-// MHD_RESULT
-// DH_get_keys_handler (const struct DH_RequestHandler *rh,
-//                      struct MHD_Connection *connection)
-// {
-//   struct DH_KeyStateHandle *ksh;
-//   json_t *reply;
-
-//   (void) rh;
-//   ksh = keys_get_state (true);
-//   if (NULL == ksh)
-//   {
-//     return TALER_MHD_reply_with_error (connection,
-//                                        MHD_HTTP_SERVICE_UNAVAILABLE,
-//                                        
TALER_EC_EXCHANGE_GENERIC_KEYS_MISSING,
-//                                        "no key state");
-//   }
-//   sync_key_helpers (ksh->helpers);
-//   if (NULL == ksh->management_keys_reply)
-//   {
-//     struct FutureBuilderContext fbc = {
-//       .ksh = ksh,
-//       .donation_units = json_array (),
-//       .signkeys = json_array ()
-//     };
-//     if ( (GNUNET_is_zero (&donation_unit_rsa_sm_pub)) &&
-//          (GNUNET_is_zero (&donation_unit_cs_sm_pub)) )
-//     {
-//       /* Either IPC failed, or neither helper had any donation_unit 
configured. */
-//       return TALER_MHD_reply_with_error (connection,
-//                                          MHD_HTTP_BAD_GATEWAY,
-//                                          
TALER_EC_EXCHANGE_DENOMINATION_HELPER_UNAVAILABLE,
-//                                          NULL);
-//     }
-//     if (GNUNET_is_zero (&esign_sm_pub))
-//     {
-//       return TALER_MHD_reply_with_error (connection,
-//                                          MHD_HTTP_BAD_GATEWAY,
-//                                          
TALER_EC_EXCHANGE_SIGNKEY_HELPER_UNAVAILABLE,
-//                                          NULL);
-//     }
-//     GNUNET_assert (NULL != fbc.donation_units);
-//     GNUNET_assert (NULL != fbc.signkeys);
-//     GNUNET_CONTAINER_multihashmap_iterate (ksh->helpers->donation_unit_keys,
-//                                            &add_donation_unitkey_cb,
-//                                            &fbc);
-//     GNUNET_CONTAINER_multipeermap_iterate (ksh->helpers->esign_keys,
-//                                            &add_signkey_cb,
-//                                            &fbc);
-//     reply = GNUNET_JSON_PACK (
-//       GNUNET_JSON_pack_array_steal ("future_donation_units",
-//                                     fbc.donation_units),
-//       GNUNET_JSON_pack_array_steal ("future_signkeys",
-//                                     fbc.signkeys),
-//       GNUNET_JSON_pack_data_auto ("donation_unit_secmod_public_key",
-//                                   &donation_unit_rsa_sm_pub),
-//       GNUNET_JSON_pack_data_auto ("donation_unit_secmod_cs_public_key",
-//                                   &donation_unit_cs_sm_pub),
-//       GNUNET_JSON_pack_data_auto ("signkey_secmod_public_key",
-//                                   &esign_sm_pub));
-//     GNUNET_log (GNUNET_ERROR_TYPE_INFO,
-//                 "Returning GET /keys response:\n");
-//     if (NULL == reply)
-//       return TALER_MHD_reply_with_error (connection,
-//                                          MHD_HTTP_INTERNAL_SERVER_ERROR,
-//                                          
TALER_EC_GENERIC_JSON_ALLOCATION_FAILURE,
-//                                          NULL);
-//     GNUNET_assert (NULL == ksh->management_keys_reply);
-//     ksh->management_keys_reply = reply;
-//   }
-//   else
-//   {
-//     reply = ksh->management_keys_reply;
-//   }
-//   return TALER_MHD_reply_json (connection,
-//                                reply,
-//                                MHD_HTTP_OK);
-// }
+//enum TALER_ErrorCode
+//DH_keys_donation_unit_cs_r_pub (
+//  const struct DH_CsDeriveData *cdd,
+//  struct GNUNET_CRYPTO_CSPublicRPairP *r_pub)
+//{
+//  const struct DONAU_DonationUnitHashP *h_donation_unit_pub = 
cdd->h_donation_unit_pub;
+//  const struct GNUNET_CRYPTO_CsSessionNonce *nonce = cdd->nonce;
+//  struct DH_KeyStateHandle *ksh;
+//  struct HelperDonationUnit *hd;
+//
+//  ksh = DH_keys_get_state ();
+//  if (NULL == ksh)
+//  {
+//    return TALER_EC_EXCHANGE_GENERIC_KEYS_MISSING;
+//  }
+//  hd = GNUNET_CONTAINER_multihashmap_get (ksh->helpers->donation_unit_keys,
+//                                          &h_donation_unit_pub->hash);
+//  if (NULL == hd)
+//  {
+//    return TALER_EC_EXCHANGE_GENERIC_DENOMINATION_KEY_UNKNOWN;
+//  }
+//  if (GNUNET_CRYPTO_BSA_CS !=
+//      hd->donation_unit_pub.bsign_pub_key->cipher)
+//  {
+//    return TALER_EC_GENERIC_INTERNAL_INVARIANT_FAILURE;
+//  }
+//
+//  {
+//    struct TALER_CRYPTO_CsDeriveRequest cdr = {
+//      .h_cs = &hd->h_details.h_cs,
+//      .nonce = nonce
+//    };
+//    return TALER_CRYPTO_helper_cs_r_derive (ksh->helpers->csdh,
+//                                            &cdr,
+//                                            r_pub);
+//  }
+//}
+
+
+//enum TALER_ErrorCode
+//DH_keys_donation_unit_cs_batch_r_pub (
+//  unsigned int cdds_length,
+//  const struct DH_CsDeriveData cdds[static cdds_length],
+//  struct GNUNET_CRYPTO_CSPublicRPairP r_pubs[static cdds_length])
+//{
+//  struct DH_KeyStateHandle *ksh;
+//  struct HelperDonationUnit *hd;
+//  struct TALER_CRYPTO_CsDeriveRequest cdrs[cdds_length];
+//
+//  ksh = DH_keys_get_state ();
+//  if (NULL == ksh)
+//  {
+//    return TALER_EC_EXCHANGE_GENERIC_KEYS_MISSING;
+//  }
+//  for (unsigned int i = 0; i<cdds_length; i++)
+//  {
+//    const struct DONAU_DonationUnitHashP *h_donation_unit_pub = 
cdds[i].h_donation_unit_pub;
+//    const struct GNUNET_CRYPTO_CsSessionNonce *nonce = cdds[i].nonce;
+//
+//    hd = GNUNET_CONTAINER_multihashmap_get (ksh->helpers->donation_unit_keys,
+//                                            &h_donation_unit_pub->hash);
+//    if (NULL == hd)
+//    {
+//      return TALER_EC_EXCHANGE_GENERIC_DENOMINATION_KEY_UNKNOWN;
+//    }
+//    if (GNUNET_CRYPTO_BSA_CS !=
+//        hd->donation_unit_pub.bsign_pub_key->cipher)
+//    {
+//      return TALER_EC_GENERIC_INTERNAL_INVARIANT_FAILURE;
+//    }
+//    cdrs[i].h_cs = &hd->h_details.h_cs;
+//    cdrs[i].nonce = nonce;
+//  }
+//
+//  return TALER_CRYPTO_helper_cs_r_batch_derive (ksh->helpers->csdh,
+//                                                cdds_length,
+//                                                cdrs,
+//                                                r_pubs);
+//}
+
+
+void
+DH_keys_donation_unit_revoke (const struct DONAU_DonationUnitHashP 
*h_donation_unit_pub)
+{
+  struct DH_KeyStateHandle *ksh;
+  struct HelperDonationUnit *hd;
+
+  ksh = DH_keys_get_state ();
+  if (NULL == ksh)
+  {
+    GNUNET_break (0);
+    return;
+  }
+  hd = GNUNET_CONTAINER_multihashmap_get (ksh->helpers->donation_unit_keys,
+                                          &h_donation_unit_pub->hash);
+  if (NULL == hd)
+  {
+    GNUNET_break (0);
+    return;
+  }
+  switch (hd->donation_unit_pub.bsign_pub_key->cipher)
+  {
+  case GNUNET_CRYPTO_BSA_INVALID:
+    break;
+  case GNUNET_CRYPTO_BSA_RSA:
+    TALER_CRYPTO_helper_rsa_revoke (ksh->helpers->rsadh,
+                                    &hd->h_details.h_rsa);
+    DH_keys_update_states ();
+    return;
+  case GNUNET_CRYPTO_BSA_CS:
+    TALER_CRYPTO_helper_cs_revoke (ksh->helpers->csdh,
+                                   &hd->h_details.h_cs);
+    DH_keys_update_states ();
+    return;
+  }
+  GNUNET_break (0);
+  return;
+}
+
+
+//enum TALER_ErrorCode
+//DH_keys_donau_sign_ (
+//  const struct GNUNET_CRYPTO_EccSignaturePurpose *purpose,
+//  struct DONAU_DonauPublicKeyP *pub,
+//  struct DONAU_DonauSignatureP *sig)
+//{
+//  struct DH_KeyStateHandle *ksh;
+//
+//  ksh = DH_keys_get_state ();
+//  if (NULL == ksh)
+//  {
+//    /* This *can* happen if the exchange's crypto helper is not running
+//       or had some bad error. */
+//    GNUNET_log (GNUNET_ERROR_TYPE_ERROR,
+//                "Cannot sign request, no valid signing keys available.\n");
+//    return TALER_EC_EXCHANGE_GENERIC_KEYS_MISSING;
+//  }
+//  return DH_keys_donau_sign2_ (ksh,
+//                                   purpose,
+//                                   pub,
+//                                   sig);
+//}
+//
+//
+//enum TALER_ErrorCode
+//DH_keys_donau_sign2_ (
+//  void *cls,
+//  const struct GNUNET_CRYPTO_EccSignaturePurpose *purpose,
+//  struct DONAU_DonauPublicKeyP *pub,
+//  struct DONAU_DonauSignatureP *sig)
+//{
+//  struct DH_KeyStateHandle *ksh = cls;
+//  enum TALER_ErrorCode ec;
+//
+//  ec = TALER_CRYPTO_helper_esign_sign_ (ksh->helpers->esh,
+//                                        purpose,
+//                                        pub,
+//                                        sig);
+//  if (TALER_EC_NONE != ec)
+//    return ec;
+//  {
+//    /* Here we check here that 'pub' is set to an exchange public key that is
+//       actually signed by the master key! Otherwise, we happily continue to
+//       use key material even if the offline signatures have not been made
+//       yet! */
+//    struct GNUNET_PeerIdentity pid;
+//    struct SigningKey *sk;
+//
+//    pid.public_key = pub->eddsa_pub;
+//    sk = GNUNET_CONTAINER_multipeermap_get (ksh->signkey_map,
+//                                            &pid);
+//    if (NULL == sk)
+//    {
+//      /* just to be safe, zero out the (valid) signature, as the key
+//         should not or no longer be used */
+//      GNUNET_log (GNUNET_ERROR_TYPE_WARNING,
+//                  "Cannot sign, offline key signatures are missing!\n");
+//      memset (sig,
+//              0,
+//              sizeof (*sig));
+//      return TALER_EC_EXCHANGE_SIGNKEY_HELPER_BUG;
+//    }
+//  }
+//  return ec;
+//}
+
+
+void
+DH_keys_donau_revoke (const struct DONAU_DonauPublicKeyP *donau_pub)
+{
+  struct DH_KeyStateHandle *ksh;
+
+  ksh = DH_keys_get_state ();
+  if (NULL == ksh)
+  {
+    GNUNET_break (0);
+    return;
+  }
+  TALER_CRYPTO_helper_esign_revoke (ksh->helpers->esh,
+                                    donau_pub);
+  DH_keys_update_states ();
+}
+
 
 /**
  * Comparator used for a binary search by cherry_pick_date for @a key in the
@@ -1242,48 +2385,9 @@ krd_search_comparator (const void *key,
 }
 
 
-/**
- * Callback used to set headers in a response.
- *
- * @param cls closure
- * @param[in,out] resp response to modify
- */
-typedef void
-(*TEH_RESPONSE_SetHeaders)(void *cls,
-                           struct MHD_Response *resp);
-
-
-MHD_RESULT
-DH_RESPONSE_reply_not_modified (
-  struct MHD_Connection *connection,
-  const char *etags,
-  TEH_RESPONSE_SetHeaders cb,
-  void *cb_cls)
-{
-  MHD_RESULT ret;
-  struct MHD_Response *resp;
-
-  resp = MHD_create_response_from_buffer (0,
-                                          NULL,
-                                          MHD_RESPMEM_PERSISTENT);
-  cb (cb_cls,
-      resp);
-  GNUNET_break (MHD_YES ==
-                MHD_add_response_header (resp,
-                                         MHD_HTTP_HEADER_ETAG,
-                                         etags));
-  ret = MHD_queue_response (connection,
-                            MHD_HTTP_NOT_MODIFIED,
-                            resp);
-  GNUNET_break (MHD_YES == ret);
-  MHD_destroy_response (resp);
-  return ret;
-}
-
-
 MHD_RESULT
 DH_keys_get_handler (struct DH_RequestContext *rc,
-                     const char *const args[])
+                      const char *const args[])
 {
   struct GNUNET_TIME_Timestamp last_issue_date;
   const char *etag;
@@ -1292,38 +2396,38 @@ DH_keys_get_handler (struct DH_RequestContext *rc,
                                       MHD_HEADER_KIND,
                                       MHD_HTTP_HEADER_IF_NONE_MATCH);
   (void) args;
-  // {
-  //   const char *have_cherrypick;
-
-  //   have_cherrypick = MHD_lookup_connection_value (rc->connection,
-  //                                                  MHD_GET_ARGUMENT_KIND,
-  //                                                  "last_issue_date");
-  //   if (NULL != have_cherrypick)
-  //   {
-  //     unsigned long long cherrypickn;
-
-  //     if (1 !=
-  //         sscanf (have_cherrypick,
-  //                 "%llu",
-  //                 &cherrypickn))
-  //     {
-  //       GNUNET_break_op (0);
-  //       return TALER_MHD_reply_with_error (rc->connection,
-  //                                          MHD_HTTP_BAD_REQUEST,
-  //                                          
TALER_EC_GENERIC_PARAMETER_MALFORMED,
-  //                                          have_cherrypick);
-  //     }
-  //     /* The following multiplication may overflow; but this should not 
really
-  //        be a problem, as giving back 'older' data than what the client 
asks for
-  //        (given that the client asks for data in the distant future) is not
-  //        problematic */
-  //     last_issue_date = GNUNET_TIME_timestamp_from_s (cherrypickn);
-  //   }
-  //   else
-  //   {
-  //     last_issue_date = GNUNET_TIME_UNIT_ZERO_TS;
-  //   }
-  // }
+  {
+    const char *have_cherrypick;
+
+    have_cherrypick = MHD_lookup_connection_value (rc->connection,
+                                                   MHD_GET_ARGUMENT_KIND,
+                                                   "last_issue_date");
+    if (NULL != have_cherrypick)
+    {
+      unsigned long long cherrypickn;
+
+      if (1 !=
+          sscanf (have_cherrypick,
+                  "%llu",
+                  &cherrypickn))
+      {
+        GNUNET_break_op (0);
+        return TALER_MHD_reply_with_error (rc->connection,
+                                           MHD_HTTP_BAD_REQUEST,
+                                           
TALER_EC_GENERIC_PARAMETER_MALFORMED,
+                                           have_cherrypick);
+      }
+      /* The following multiplication may overflow; but this should not really
+         be a problem, as giving back 'older' data than what the client asks 
for
+         (given that the client asks for data in the distant future) is not
+         problematic */
+      last_issue_date = GNUNET_TIME_timestamp_from_s (cherrypickn);
+    }
+    else
+    {
+      last_issue_date = GNUNET_TIME_UNIT_ZERO_TS;
+    }
+  }
 
   {
     struct DH_KeyStateHandle *ksh;
@@ -1375,10 +2479,10 @@ DH_keys_get_handler (struct DH_RequestContext *rc,
     if ( (NULL != etag) &&
          (0 == strcmp (etag,
                        krd->etag)) )
-      return DH_RESPONSE_reply_not_modified (rc->connection,
-                                             krd->etag,
-                                             &setup_general_response_headers,
-                                             ksh);
+      //return DH_RESPONSE_reply_not_modified (rc->connection,
+      //                                        krd->etag,
+      //                                        
&setup_general_response_headers,
+      //                                        ksh);
 
     return MHD_queue_response (rc->connection,
                                MHD_HTTP_OK,
@@ -1390,4 +2494,251 @@ DH_keys_get_handler (struct DH_RequestContext *rc,
 }
 
 
+enum GNUNET_GenericReturnValue
+DH_keys_get_timing (const struct DONAU_DonauPublicKeyP *donau_pub,
+                     struct DONAUDB_SignkeyMetaData *meta)
+{
+  struct DH_KeyStateHandle *ksh;
+  struct HelperSignkey *hsk;
+  struct GNUNET_PeerIdentity pid;
+
+  ksh = DH_keys_get_state_for_management_only ();
+  if (NULL == ksh)
+  {
+    GNUNET_break (0);
+    return GNUNET_SYSERR;
+  }
+
+  pid.public_key = donau_pub->eddsa_pub;
+  hsk = GNUNET_CONTAINER_multipeermap_get (ksh->helpers->esign_keys,
+                                           &pid);
+  if (NULL == hsk)
+  {
+    GNUNET_break (0);
+    return GNUNET_NO;
+  }
+  meta->start = hsk->start_time;
+
+  //meta->expire_sign = GNUNET_TIME_absolute_to_timestamp (
+  //  GNUNET_TIME_absolute_add (meta->start.abs_time,
+  //                            hsk->validity_duration));
+  //meta->expire_legal = GNUNET_TIME_absolute_to_timestamp (
+  //  GNUNET_TIME_absolute_add (meta->expire_sign.abs_time,
+  //                            signkey_legal_duration));
+  return GNUNET_OK;
+}
+
+
+/**
+ * Closure for #add_future_donation_unitkey_cb and #add_future_signkey_cb.
+ */
+struct FutureBuilderContext
+{
+  /**
+   * Our key state.
+   */
+  struct DH_KeyStateHandle *ksh;
+
+  /**
+   * Array of donation_unit keys.
+   */
+  json_t *donation_units;
+
+  /**
+   * Array of signing keys.
+   */
+  json_t *signkeys;
+
+};
+
+
+/**
+ * Function called on all of our current and future donation_unit keys
+ * known to the helper process. Filters out those that are current
+ * and adds the remaining donation_unit keys (with their configuration
+ * data) to the JSON array.
+ *
+ * @param cls the `struct FutureBuilderContext *`
+ * @param h_donation_unit_pub hash of the donation_unit public key
+ * @param value a `struct HelperDonationUnit`
+ * @return #GNUNET_OK (continue to iterate)
+ */
+static enum GNUNET_GenericReturnValue
+add_future_donation_unitkey_cb (void *cls,
+                        const struct GNUNET_HashCode *h_donation_unit_pub,
+                        void *value)
+{
+  struct FutureBuilderContext *fbc = cls;
+  struct HelperDonationUnit *hd = value;
+  struct DH_DonationUnitKey *dk;
+  struct DONAUDB_DonationUnitKeyMetaData meta = {0};
+
+  dk = GNUNET_CONTAINER_multihashmap_get (fbc->ksh->donation_unitkey_map,
+                                          h_donation_unit_pub);
+  if (NULL != dk)
+    return GNUNET_OK; /* skip: this key is already active! */
+  if (GNUNET_TIME_relative_is_zero (hd->validity_duration))
+    return GNUNET_OK; /* this key already expired! */
+  //meta.start = hd->start_time;
+  //meta.expire_withdraw = GNUNET_TIME_absolute_to_timestamp (
+  //  GNUNET_TIME_absolute_add (meta.start.abs_time,
+  //                            hd->validity_duration));
+
+  //GNUNET_assert (
+  //  0 ==
+  //  json_array_append_new (
+  //    fbc->donation_units,
+  //    GNUNET_JSON_PACK (
+  //      //DONAU_JSON_pack_amount ("value",
+  //      //                        &meta.value),
+  //      //GNUNET_JSON_pack_timestamp ("stamp_start",
+  //      //                            meta.start),
+  //      //GNUNET_JSON_pack_timestamp ("stamp_expire_withdraw",
+  //      //                            meta.expire_withdraw),
+  //      //GNUNET_JSON_pack_timestamp ("stamp_expire_deposit",
+  //      //                            meta.expire_deposit),
+  //      //GNUNET_JSON_pack_timestamp ("stamp_expire_legal",
+  //      //                            meta.expire_legal),
+  //      DONAU_JSON_pack_donation_unit_pub ("donation_unit_pub",
+  //                                 &hd->donation_unit_pub),
+  //      GNUNET_JSON_pack_data_auto ("donation_unit_secmod_sig",
+  //                                  &hd->sm_sig),
+  //      GNUNET_JSON_pack_string ("section_name",
+  //                               hd->section_name))));
+  return GNUNET_OK;
+}
+
+
+/**
+ * Function called on all of our current and future exchange signing keys
+ * known to the helper process. Filters out those that are current
+ * and adds the remaining signing keys (with their configuration
+ * data) to the JSON array.
+ *
+ * @param cls the `struct FutureBuilderContext *`
+ * @param pid actually the exchange public key (type disguised)
+ * @param value a `struct HelperDonationUnit`
+ * @return #GNUNET_OK (continue to iterate)
+ */
+static enum GNUNET_GenericReturnValue
+add_future_signkey_cb (void *cls,
+                       const struct GNUNET_PeerIdentity *pid,
+                       void *value)
+{
+  struct FutureBuilderContext *fbc = cls;
+  struct HelperSignkey *hsk = value;
+  struct SigningKey *sk;
+  struct GNUNET_TIME_Timestamp stamp_expire;
+  struct GNUNET_TIME_Timestamp legal_end;
+
+  sk = GNUNET_CONTAINER_multipeermap_get (fbc->ksh->signkey_map,
+                                          pid);
+  if (NULL != sk)
+    return GNUNET_OK; /* skip: this key is already active */
+  if (GNUNET_TIME_relative_is_zero (hsk->validity_duration))
+    return GNUNET_OK; /* this key already expired! */
+  stamp_expire = GNUNET_TIME_absolute_to_timestamp (
+    GNUNET_TIME_absolute_add (hsk->start_time.abs_time,
+                              hsk->validity_duration));
+  legal_end = GNUNET_TIME_absolute_to_timestamp (
+    GNUNET_TIME_absolute_add (stamp_expire.abs_time,
+                              signkey_legal_duration));
+  GNUNET_assert (0 ==
+                 json_array_append_new (
+                   fbc->signkeys,
+                   GNUNET_JSON_PACK (
+                     GNUNET_JSON_pack_data_auto ("key",
+                                                 &hsk->donau_pub),
+                     GNUNET_JSON_pack_timestamp ("stamp_start",
+                                                 hsk->start_time),
+                     GNUNET_JSON_pack_timestamp ("stamp_expire",
+                                                 stamp_expire),
+                     GNUNET_JSON_pack_timestamp ("stamp_end",
+                                                 legal_end),
+                     GNUNET_JSON_pack_data_auto ("signkey_secmod_sig",
+                                                 &hsk->sm_sig))));
+  return GNUNET_OK;
+}
+
+
+MHD_RESULT
+DH_keys_management_get_keys_handler (const struct DH_RequestHandler *rh,
+                                      struct MHD_Connection *connection)
+{
+  struct DH_KeyStateHandle *ksh;
+  json_t *reply;
+
+  (void) rh;
+  ksh = DH_keys_get_state_for_management_only ();
+  if (NULL == ksh)
+  {
+    return TALER_MHD_reply_with_error (connection,
+                                       MHD_HTTP_SERVICE_UNAVAILABLE,
+                                       TALER_EC_EXCHANGE_GENERIC_KEYS_MISSING,
+                                       "no key state");
+  }
+  sync_key_helpers (ksh->helpers);
+  if (NULL == ksh->management_keys_reply)
+  {
+    struct FutureBuilderContext fbc = {
+      .ksh = ksh,
+      .donation_units = json_array (),
+      .signkeys = json_array ()
+    };
+
+    if ( (GNUNET_is_zero (&donation_unit_rsa_sm_pub)) &&
+         (GNUNET_is_zero (&donation_unit_cs_sm_pub)) )
+    {
+      /* Either IPC failed, or neither helper had any donation_units 
configured. */
+      return TALER_MHD_reply_with_error (connection,
+                                         MHD_HTTP_BAD_GATEWAY,
+                                         
TALER_EC_EXCHANGE_DENOMINATION_HELPER_UNAVAILABLE,
+                                         NULL);
+    }
+    if (GNUNET_is_zero (&esign_sm_pub))
+    {
+      return TALER_MHD_reply_with_error (connection,
+                                         MHD_HTTP_BAD_GATEWAY,
+                                         
TALER_EC_EXCHANGE_SIGNKEY_HELPER_UNAVAILABLE,
+                                         NULL);
+    }
+    GNUNET_assert (NULL != fbc.donation_units);
+    GNUNET_assert (NULL != fbc.signkeys);
+    GNUNET_CONTAINER_multihashmap_iterate (ksh->helpers->donation_unit_keys,
+                                           &add_future_donation_unitkey_cb,
+                                           &fbc);
+    GNUNET_CONTAINER_multipeermap_iterate (ksh->helpers->esign_keys,
+                                           &add_future_signkey_cb,
+                                           &fbc);
+    reply = GNUNET_JSON_PACK (
+      GNUNET_JSON_pack_array_steal ("future_donation_units",
+                                    fbc.donation_units),
+      GNUNET_JSON_pack_array_steal ("future_signkeys",
+                                    fbc.signkeys),
+      GNUNET_JSON_pack_data_auto ("donation_unit_secmod_public_key",
+                                  &donation_unit_rsa_sm_pub),
+      GNUNET_JSON_pack_data_auto ("donation_unit_secmod_cs_public_key",
+                                  &donation_unit_cs_sm_pub),
+      GNUNET_JSON_pack_data_auto ("signkey_secmod_public_key",
+                                  &esign_sm_pub));
+    GNUNET_log (GNUNET_ERROR_TYPE_INFO,
+                "Returning GET /management/keys response:\n");
+    if (NULL == reply)
+      return TALER_MHD_reply_with_error (connection,
+                                         MHD_HTTP_INTERNAL_SERVER_ERROR,
+                                         
TALER_EC_GENERIC_JSON_ALLOCATION_FAILURE,
+                                         NULL);
+    GNUNET_assert (NULL == ksh->management_keys_reply);
+    ksh->management_keys_reply = reply;
+  }
+  else
+  {
+    reply = ksh->management_keys_reply;
+  }
+  return TALER_MHD_reply_json (connection,
+                               reply,
+                               MHD_HTTP_OK);
+}
+
+
 /* end of donau-httpd_keys.c */
diff --git a/src/donau/donau-httpd_keys.h b/src/donau/donau-httpd_keys.h
index ee606bc..a6d26c5 100644
--- a/src/donau/donau-httpd_keys.h
+++ b/src/donau/donau-httpd_keys.h
@@ -1,150 +1,262 @@
 /*
   This file is part of TALER
-  Copyright (C) 2020-2023 Taler Systems SA
+  Copyright (C) 2020-2022 Taler Systems SA
 
   TALER is free software; you can redistribute it and/or modify it under the
   terms of the GNU Affero General Public License as published by the Free 
Software
   Foundation; either version 3, or (at your option) any later version.
 
   TALER is distributed in the hope that it will be useful, but WITHOUT ANY
-  WARRANTY; without even the implied warranty of CHARITYABILITY or FITNESS FOR
+  WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR
   A PARTICULAR PURPOSE.  See the GNU Affero General Public License for more 
details.
 
   You should have received a copy of the GNU Affero General Public License 
along with
   TALER; see the file COPYING.  If not, see <http://www.gnu.org/licenses/>
 */
 /**
- * @file donau-httpd_keys.h
+ * @file taler-donau-httpd_keys.h
  * @brief management of our various keys
  * @author Christian Grothoff
  */
 #include "taler/platform.h"
 #include "taler/taler_json_lib.h"
 #include "taler/taler_mhd_lib.h"
-// #include "donau-httpd_responses.h"
+//#include "taler/taler-donau-httpd_responses.h"
 #include "donau_util.h"
 #include "donaudb_plugin.h"
 #include "donau-httpd.h"
 
-
 #ifndef DONAU_HTTPD_KEYS_H
 #define DONAU_HTTPD_KEYS_H
 
 
 /**
- * @brief All information about a donation unit key (which is used to
- * sign donation receipts into existence).
+ * @brief All information about a donation_unit key (which is used to
+ * sign coins into existence).
  */
 struct DH_DonationUnitKey
 {
 
   /**
-   * Decoded donation unit public key (the hash of it is in
+   * Decoded donation_unit public key (the hash of it is in
    * @e issue, but we sometimes need the full public key as well).
    */
   struct DONAU_DonationUnitPublicKey donation_unit_pub;
 
   /**
-   * Hash code of the donation unit public key.
+   * Hash code of the donation_unit public key.
    */
   struct DONAU_DonationUnitHashP h_donation_unit_pub;
 
   /**
-   * Meta data about the type of the donation unit, containing the validity
-   * year and the value of the donation unit.
+   * Meta data about the type of the donation_unit, such as fees and validity
+   * periods.
    */
   struct DONAUDB_DonationUnitKeyMetaData meta;
 
 };
 
 /**
- * Information needed to create a blind signature.
+ * Snapshot of the (coin and signing) keys (including private keys) of
+ * the donau.  There can be multiple instances of this struct, as it is
+ * reference counted and only destroyed once the last user is done
+ * with it.  The current instance is acquired using
+ * #DH_KS_acquire().  Using this function increases the
+ * reference count.  The contents of this structure (except for the
+ * reference counter) should be considered READ-ONLY until it is
+ * ultimately destroyed (as there can be many concurrent users).
+ */
+struct DH_KeyStateHandle;
+
+
+/**
+ * Run internal invariant checks. For debugging.
+ */
+void
+DH_check_invariants (void);
+
+/**
+ * Clean up wire subsystem.
  */
-// struct DH_CoinSignData
-// {
+void
+DH_wire_done (void);
+
 /**
+ * Initialize wire subsystem.
+ *
+ * @return #GNUNET_OK on success
+ */
+enum GNUNET_GenericReturnValue
+DH_wire_init (void);
+
+
+/**
+ * Something changed in the database. Rebuild the wire replies.  This function
+ * should be called if the donau learns about a new signature from our
+ * master key.
+ *
+ * (We do not do so immediately, but merely signal to all threads that they
+ * need to rebuild their wire state upon the next call to
+ * #DH_keys_get_state()).
+ */
+void
+DH_wire_update_state (void);
+
+
+/**
+ * Return the current key state for this thread.  Possibly re-builds the key
+ * state if we have reason to believe that something changed.
+ *
+ * The result is ONLY valid until the next call to
+ * #DH_keys_donation_unit_by_hash() or #DH_keys_get_state()
+ * or #DH_keys_donau_sign().
+ *
+ * @return NULL on error
+ */
+struct DH_KeyStateHandle *
+DH_keys_get_state (void);
+
+/**
+ * Obtain the key state if we should NOT run finish_keys_response() because we
+ * only need the state for the /management/keys API
+ */
+struct DH_KeyStateHandle *
+DH_keys_get_state_for_management_only (void);
+
+/**
+ * Something changed in the database. Rebuild all key states.  This function
+ * should be called if the donau learns about a new signature from an
+ * auditor or our master key.
+ *
+ * (We do not do so immediately, but merely signal to all threads that they
+ * need to rebuild their key state upon the next call to
+ * #DH_keys_get_state()).
+ */
+void
+DH_keys_update_states (void);
+
+
+/**
+ * Look up the issue for a denom public key.  Note that the result
+ * must only be used in this thread and only until another key or
+ * key state is resolved.
+ *
+ * @param h_donation_unit_pub hash of donation_unit public key
+ * @param[in,out] conn used to return status message if NULL is returned
+ * @param[out] mret set to the MHD status if NULL is returned
+ * @return the donation_unit key issue,
+ *         or NULL if @a h_donation_unit_pub could not be found
+ */
+struct DH_DonationUnitKey *
+DH_keys_donation_unit_by_hash (
+  const struct DONAU_DonationUnitHashP *h_donation_unit_pub,
+  struct MHD_Connection *conn,
+  MHD_RESULT *mret);
+
+
+/**
+ * Look up the issue for a denom public key using a given @a ksh.  This allows
+ * requesting multiple donation_units with the same @a ksh which thus will
+ * remain valid until the next call to #DH_keys_donation_unit_by_hash() or
+ * #DH_keys_get_state() or #DH_keys_donau_sign().
+ *
+ * @param ksh key state state to look in
+ * @param h_donation_unit_pub hash of donation_unit public key
+ * @param[in,out] conn connection used to return status message if NULL is 
returned
+ * @param[out] mret set to the MHD status if NULL is returned
+ * @return the donation_unit key issue,
+ *         or NULL if @a h_donation_unit_pub could not be found
+ */
+struct DH_DonationUnitKey *
+DH_keys_donation_unit_by_hash_from_state (
+  const struct DH_KeyStateHandle *ksh,
+  const struct DONAU_DonationUnitHashP *h_donation_unit_pub,
+  struct MHD_Connection *conn,
+  MHD_RESULT *mret);
+
+/**
+ * Information needed to create a blind signature.
+ */
+struct DH_CoinSignData
+{
+  /**
    * Hash of key to sign with.
    */
-// const struct TALER_DenominationHashP *h_denom_pub;
+  const struct DONAU_DonationUnitHashP *h_donation_unit_pub;
 
-/**
+  /**
    * Blinded planchet to sign over.
    */
-// const struct TALER_BlindedPlanchet *bp;
-// };
-
-
-// /**
-//  * Request to sign @a csds.
-//  *
-//  * @param csds array with data to blindly sign (and keys to sign with)
-//  * @param csds_length length of @a csds array
-//  * @param for_melt true if this is for a melt operation
-//  * @param[out] bss array set to the blind signature on success; must be of 
length @a csds_length
-//  * @return #TALER_EC_NONE on success
-//  */
-// enum TALER_ErrorCode
-// TEH_keys_denomination_batch_sign (
-//   unsigned int csds_length,
-//   const struct TEH_CoinSignData csds[static csds_length],
-//   bool for_melt,
-//   struct TALER_BlindedDenominationSignature bss[static csds_length]);
-
-
-// /**
-//  * Information needed to derive the CS r_pub.
-//  */
-// struct TEH_CsDeriveData
-// {
-//   /**
-//    * Hash of key to sign with.
-//    */
-//   const struct TALER_DenominationHashP *h_denom_pub;
-
-//   /**
-//    * Nonce to use.
-//    */
-//   const struct GNUNET_CRYPTO_CsSessionNonce *nonce;
-// };
-
-
-// /**
-//  * Request to derive CS @a r_pub using the denomination and nonce from @a 
cdd.
-//  *
-//  * @param cdd data to compute @a r_pub from
-//  * @param for_melt true if this is for a melt operation
-//  * @param[out] r_pub where to write the result
-//  * @return #TALER_EC_NONE on success
-//  */
-// enum TALER_ErrorCode
-// TEH_keys_denomination_cs_r_pub (
-//   const struct TEH_CsDeriveData *cdd,
-//   bool for_melt,
-//   struct GNUNET_CRYPTO_CSPublicRPairP *r_pub);
-
-// /**
-//  * Request to derive a bunch of CS @a r_pubs using the
-//  * denominations and nonces from @a cdds.
-//  *
-//  * @param cdds array to compute @a r_pubs from
-//  * @param cdds_length length of the @a cdds array
-//  * @param for_melt true if this is for a melt operation
-//  * @param[out] r_pubs array where to write the result; must be of length @a 
cdds_length
-//  * @return #TALER_EC_NONE on success
-//  */
-// enum TALER_ErrorCode
-// TEH_keys_denomination_cs_batch_r_pub (
-//   unsigned int cdds_length,
-//   const struct TEH_CsDeriveData cdds[static cdds_length],
-//   bool for_melt,
-//   struct GNUNET_CRYPTO_CSPublicRPairP r_pubs[static cdds_length]);
+  const struct DONAU_BlindedDonationUnit *bp;
+};
+
+
+/**
+ * Request to sign @a csds.
+ *
+ * @param csds array with data to blindly sign (and keys to sign with)
+ * @param csds_length length of @a csds array
+ * @param[out] bss array set to the blind signature on success; must be of 
length @a csds_length
+ * @return #TALER_EC_NONE on success
+ */
+enum TALER_ErrorCode
+DH_keys_donation_unit_batch_sign (
+  unsigned int csds_length,
+  const struct DH_CoinSignData csds[static csds_length],
+  struct DONAU_BlindedDonationUnitSignature bss[static csds_length]);
+
+
+/**
+ * Information needed to derive the CS r_pub.
+ */
+struct DH_CsDeriveData
+{
+  /**
+   * Hash of key to sign with.
+   */
+  const struct DONAU_DonationUnitHashP *h_donation_unit_pub;
+
+  /**
+   * Nonce to use.
+   */
+  const struct GNUNET_CRYPTO_CsSessionNonce *nonce;
+};
+
+
+/**
+ * Request to derive CS @a r_pub using the donation_unit and nonce from @a cdd.
+ *
+ * @param cdd data to compute @a r_pub from
+ * @param[out] r_pub where to write the result
+ * @return #TALER_EC_NONE on success
+ */
+enum TALER_ErrorCode
+DH_keys_donation_unit_cs_r_pub (
+  const struct DH_CsDeriveData *cdd,
+  struct GNUNET_CRYPTO_CSPublicRPairP *r_pub);
+
+
+/**
+ * Request to derive a bunch of CS @a r_pubs using the
+ * donation_units and nonces from @a cdds.
+ *
+ * @param cdds array to compute @a r_pubs from
+ * @param cdds_length length of the @a cdds array
+ * @param[out] r_pubs array where to write the result; must be of length @a 
cdds_length
+ * @return #TALER_EC_NONE on success
+ */
+enum TALER_ErrorCode
+DH_keys_donation_unit_cs_batch_r_pub (
+  unsigned int cdds_length,
+  const struct DH_CsDeriveData cdds[static cdds_length],
+  struct GNUNET_CRYPTO_CSPublicRPairP r_pubs[static cdds_length]);
 
 
 /**
  * Fully clean up keys subsystem.
  */
 void
-TEH_keys_finished (void);
+DH_keys_finished (void);
 
 
 /**
@@ -154,7 +266,110 @@ TEH_keys_finished (void);
  * @param do_shutdown are we shutting down?
  */
 void
-TEH_resume_keys_requests (bool do_shutdown);
+DH_resume_keys_requests (bool do_shutdown);
+
+
+/**
+ * Sign the message in @a purpose with the donau's signing key.
+ *
+ * The @a purpose data is the beginning of the data of which the signature is
+ * to be created. The `size` field in @a purpose must correctly indicate the
+ * number of bytes of the data structure, including its header.  Use
+ * #DH_keys_donau_sign() instead of calling this function directly!
+ *
+ * @param purpose the message to sign
+ * @param[out] pub set to the current public signing key of the donau
+ * @param[out] sig signature over purpose using current signing key
+ * @return #TALER_EC_NONE on success
+ */
+enum TALER_ErrorCode
+DH_keys_donau_sign_ (
+  const struct GNUNET_CRYPTO_EccSignaturePurpose *purpose,
+  struct DONAU_DonauPublicKeyP *pub,
+  struct DONAU_DonauSignatureP *sig);
+
+
+/**
+ * Sign the message in @a purpose with the donau's signing key.
+ *
+ * The @a purpose data is the beginning of the data of which the signature is
+ * to be created. The `size` field in @a purpose must correctly indicate the
+ * number of bytes of the data structure, including its header.  Use
+ * #DH_keys_donau_sign() instead of calling this function directly!
+ *
+ * @param cls key state state to look in
+ * @param purpose the message to sign
+ * @param[out] pub set to the current public signing key of the donau
+ * @param[out] sig signature over purpose using current signing key
+ * @return #TALER_EC_NONE on success
+ */
+enum TALER_ErrorCode
+DH_keys_donau_sign2_ (
+  void *cls,
+  const struct GNUNET_CRYPTO_EccSignaturePurpose *purpose,
+  struct DONAU_DonauPublicKeyP *pub,
+  struct DONAU_DonauSignatureP *sig);
+
+
+/**
+ * @ingroup crypto
+ * @brief EdDSA sign a given block.
+ *
+ * The @a ps data must be a fixed-size struct for which the signature is to be
+ * created. The `size` field in @a ps->purpose must correctly indicate the
+ * number of bytes of the data structure, including its header.
+ *
+ * @param ps packed struct with what to sign, MUST begin with a purpose
+ * @param[out] pub where to store the public key to use for the signing
+ * @param[out] sig where to write the signature
+ * @return #TALER_EC_NONE on success
+ */
+#define DH_keys_donau_sign(ps,pub,sig) \
+  ({                                                  \
+    /* check size is set correctly */                 \
+    GNUNET_assert (htonl ((ps)->purpose.size) ==      \
+                   sizeof (*ps));                     \
+    /* check 'ps' begins with the purpose */          \
+    GNUNET_static_assert (((void*) (ps)) ==           \
+                          ((void*) &(ps)->purpose));  \
+    DH_keys_donau_sign_ (&(ps)->purpose,          \
+                             pub,                     \
+                             sig);                    \
+  })
+
+
+/**
+ * @ingroup crypto
+ * @brief EdDSA sign a given block.
+ *
+ * The @a ps data must be a fixed-size struct for which the signature is to be
+ * created. The `size` field in @a ps->purpose must correctly indicate the
+ * number of bytes of the data structure, including its header.
+ *
+ * This allows requesting multiple donation_units with the same @a ksh which
+ * thus will remain valid until the next call to
+ * #DH_keys_donation_unit_by_hash() or #DH_keys_get_state() or
+ * #DH_keys_donau_sign().
+ *
+ * @param ksh key state to use
+ * @param ps packed struct with what to sign, MUST begin with a purpose
+ * @param[out] pub where to store the public key to use for the signing
+ * @param[out] sig where to write the signature
+ * @return #TALER_EC_NONE on success
+ */
+#define DH_keys_donau_sign2(ksh,ps,pub,sig)       \
+  ({                                                  \
+    /* check size is set correctly */                 \
+    GNUNET_assert (htonl ((ps)->purpose.size) ==      \
+                   sizeof (*ps));                     \
+    /* check 'ps' begins with the purpose */          \
+    GNUNET_static_assert (((void*) (ps)) ==           \
+                          ((void*) &(ps)->purpose));  \
+    DH_keys_donau_sign2_ (ksh,                    \
+                              &(ps)->purpose,         \
+                              pub,                     \
+                              sig);                    \
+  })
 
 
 /**
@@ -167,7 +382,32 @@ TEH_resume_keys_requests (bool do_shutdown);
  */
 MHD_RESULT
 DH_keys_get_handler (struct DH_RequestContext *rc,
-                     const char *const args[]);
+                      const char *const args[]);
+
+
+/**
+ * Function to call to handle requests to "/management/keys" by sending
+ * back our future key material.
+ *
+ * @param rh context of the handler
+ * @param connection the MHD connection to handle
+ * @return MHD result code
+ */
+MHD_RESULT
+DH_keys_management_get_keys_handler (const struct DH_RequestHandler *rh,
+                                      struct MHD_Connection *connection);
+
+
+/**
+ * Load expiration times for the given onling signing key.
+ *
+ * @param donau_pub the online signing key
+ * @param[out] meta set to meta data about the key
+ * @return #GNUNET_OK on success
+ */
+enum GNUNET_GenericReturnValue
+DH_keys_get_timing (const struct DONAU_DonauPublicKeyP *donau_pub,
+                     struct DONAUDB_SignkeyMetaData *meta);
 
 
 /**
@@ -176,7 +416,7 @@ DH_keys_get_handler (struct DH_RequestContext *rc,
  * @return #GNUNET_OK on success
  */
 enum GNUNET_GenericReturnValue
-TEH_keys_init (void);
+DH_keys_init (void);
 
 
 #endif

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