[gnunet] branch master updated: CRYPTO: Improve comments for ECC DH

[gnunet]

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martin-schanzenbach pushed a commit to branch master
in repository gnunet.

The following commit(s) were added to refs/heads/master by this push:
     new 93b049ebd CRYPTO: Improve comments for ECC DH
93b049ebd is described below

commit 93b049ebd15a2658593fdf5d93672719fb51f4dd
Author: Martin Schanzenbach <schanzen@gnunet.org>
AuthorDate: Tue Feb 27 20:17:18 2024 +0100

    CRYPTO: Improve comments for ECC DH
    
    NEWS:-
---
 src/include/gnunet_crypto_lib.h | 14 ++++++++++++++
 1 file changed, 14 insertions(+)

diff --git a/src/include/gnunet_crypto_lib.h b/src/include/gnunet_crypto_lib.h
index f508d02f6..2c7e92fbd 100644
--- a/src/include/gnunet_crypto_lib.h
+++ b/src/include/gnunet_crypto_lib.h
@@ -1677,6 +1677,9 @@ GNUNET_CRYPTO_edx25519_key_create_from_seed (
 /**
  * @ingroup crypto
  * Create a new private key.  Clear with #GNUNET_CRYPTO_ecdhe_key_clear().
+ * This is X25519 DH (RFC 7748 Section 5) and corresponds to
+ * X25519(a,9).
+ * See #GNUNET_CRYPTO_ecc_ecdh for the DH function.
  *
  * @param[out] pk set to fresh private key;
  */
@@ -1962,6 +1965,9 @@ GNUNET_CRYPTO_ecc_scalar_from_int (int64_t val,
 /**
  * @ingroup crypto
  * Derive key material from a public and a private ECC key.
+ * This is X25519 DH (RFC 7748 Section 5) and corresponds to
+ * H(X25519(b,X25519(a,9))) where b := priv, pub := X25519(a,9),
+ * and a := #GNUNET_CRYPTO_ecdhe_key_create().
  *
  * @param priv private key to use for the ECDH (x)
  * @param pub public key to use for the ECDH (yG)
@@ -1978,6 +1984,10 @@ GNUNET_CRYPTO_ecc_ecdh (const struct 
GNUNET_CRYPTO_EcdhePrivateKey *priv,
  * @ingroup crypto
  * Derive key material from a ECDH public key and a private EdDSA key.
  * Dual to #GNUNET_CRRYPTO_ecdh_eddsa.
+ * This uses the Ed25519 private seed as X25519 seed.
+ * As such, this also is a X25519 DH (see #GNUNET_CRYPTO_ecc_ecdh).
+ * NOTE: Whenever you can get away with it, use separate key pairs
+ * for signing and encryption (DH)!
  *
  * @param priv private key from EdDSA to use for the ECDH (x)
  * @param pub public key to use for the ECDH (yG)
@@ -2126,6 +2136,10 @@ GNUNET_CRYPTO_ecdsa_ecdh (const struct 
GNUNET_CRYPTO_EcdsaPrivateKey *priv,
  * @ingroup crypto
  * Derive key material from a EdDSA public key and a private ECDH key.
  * Dual to #GNUNET_CRRYPTO_eddsa_ecdh.
+ * This converts the Edwards25519 public key @a pub to a Curve25519
+ * public key before computing a X25519 DH (see #GNUNET_CRYPTO_ecc_ecdh).
+ * NOTE: Whenever you can get away with it, use separate key pairs
+ * for signing and encryption (DH)!
  *
  * @param priv private key to use for the ECDH (y)
  * @param pub public key from EdDSA to use for the ECDH (X=h(x)G)

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