[taler-donau] branch master updated: [doc] correction blinding process

[gnunet]

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

lukas-matyja pushed a commit to branch master
in repository donau.

The following commit(s) were added to refs/heads/master by this push:
     new 1a7c92f  [doc] correction blinding process
1a7c92f is described below

commit 1a7c92fd88d2beb014a652d471ec4ffc261468f3
Author: Matyja Lukas Adam <lukas.matyja@students.bfh.ch>
AuthorDate: Tue Oct 17 09:59:04 2023 +0200

    [doc] correction blinding process
---
 doc/flows/Makefile    |   3 +-
 doc/flows/main.tex    |  12 ++--
 doc/flows/mainOld.tex | 150 ++++++++++++++++++++++++++++++++++++++++++++++++++
 3 files changed, 156 insertions(+), 9 deletions(-)

diff --git a/doc/flows/Makefile b/doc/flows/Makefile
index f00cb0c..337dc03 100644
--- a/doc/flows/Makefile
+++ b/doc/flows/Makefile
@@ -1,5 +1,4 @@
 all:
        pdflatex main.tex
-
 clean:
-       rm *.aux *.log *.pdf
+       rm *.aux *.log *.pdf 
diff --git a/doc/flows/main.tex b/doc/flows/main.tex
index 749bca4..eee6d38 100644
--- a/doc/flows/main.tex
+++ b/doc/flows/main.tex
@@ -21,15 +21,13 @@
 
 \section{Definitions}
 \begin{itemize}
-  \item \textbf{Cryptographic Hash Function} $H$
+  \item \textbf{Cryptographic Hash Function} = $H$
 
   \item \textbf{Signing Function} $Sign$
 
-  \item \textbf{Blind Signing Function} $BSign$
-
   \item \textbf{Signature} $S$
 
-  \item \textbf{Blind Signature} $B$
+  \item \textbf{Blind Signature} $BS$
 
   \item \textbf{Blinding Factor} $b$
 
@@ -69,7 +67,7 @@
   \item The donor blinds the $UDI$'s using a \textbf{different} blinding 
factor $b$ for every $UDI$.
 
   \begin{align}
-      B_{UDI} &= BSign(b,UDI, K_{pub}) \\
+      B_{UDI} &= blind(b,UDI, K_{pub}) \\
       BUDI &= \langle B_{UDI}, H(K_{priv}) \rangle
   \end{align}
 
@@ -100,7 +98,7 @@
       \item blind signs all the $BUDI$'s using the $DU$ private keys 
$K_{priv}$ matching the public keys used in $H(K_{pub})$.
 
         \begin{align}
-            S_D = Sign(BUDI, K_{priv})
+            BS_D = Sign(BUDI, K_{priv})
         \end{align}
 
     \item sends back the blind signatures ($S_D$'s) to the charity.
@@ -111,7 +109,7 @@
   \item The donor unblinds the $BUDI$'s to get the signed $UDI$'s. This 
results in the \textbf{Donation Receipt} $DR$ consisting of the $UDI$, the 
signature $S_{UDI}$ and the Hash of the $DU$ public key $H(K_{pub})$.
 
   \begin{align}
-      S_{UDI} &= B^{-1}(BUDI, S_D, b) \\
+      S_{UDI} &= unblind(BS_D, b) \\
       DR &= \langle UDI, S_{UDI}, H(K_{pub}) \rangle
   \end{align}
 \end{enumerate}
diff --git a/doc/flows/mainOld.tex b/doc/flows/mainOld.tex
new file mode 100644
index 0000000..5ac84e6
--- /dev/null
+++ b/doc/flows/mainOld.tex
@@ -0,0 +1,150 @@
+\documentclass{article}
+
+\usepackage[english]{babel}
+\usepackage[utf8]{inputenc}
+\usepackage{amsmath,amssymb}
+\usepackage{parskip}
+\usepackage{graphicx}
+\graphicspath{ {./images/} }
+
+% Margins
+\usepackage[top=3cm, left=3cm, right=3cm, bottom=3cm]{geometry}
+% Colour table cells
+\usepackage[table]{xcolor}
+
+\title{DONAU protocol overview}
+\author{Johannes Casaburi \and Pius Loosli \and Lukas Matyja}
+\date{\today}
+
+\begin{document}
+\maketitle
+
+\section{Definitions}
+\begin{itemize}
+\item $DU :=$ \textbf{donation unit} = Smallest structure representing a 
donation confirmation unit, i.e. accepted values that compose a donation 
(examples: CHF1, CHF2, EUR1, EUR2). Equivalent in Taler is "denomination".
+  \item $UDID := $ \textbf{unique donor identifier} of a donor by tax ID, made 
unique per donation to obtain unique $DR$s per donation
+  \item $BDID :=$ blinded $UDID$, blinded for privacy of the donor
+  \item $BS :=$ BDU blinded signature made with a donation unit secret key 
(from DONAU)
+  \item $S :=$ unblinded BS
+  \item $DR :=$ \textbf{donation receipt} = $UDID$ with $S$ signature of DONAU 
affirming donation over the respectiv amount as given by the DU associated with 
the signature
+  \item $DRs :=$ collection of $DR$s
+  \item $DS_{year} :=$ \textbf{donation statement} = confirmation over the 
total amount of DRs produced for a specific year and specific donor (DID)
+  \item $b :=$ blinding factor
+  \item $H :=$ cryptographic hash function
+  \item $DUi, Si, DRi, \ldots$ := number entities if there are more than one 
e.g. $DU1$, $DU2$ ...
+  \item $BS_{kj}$ or $S_{kj} \Rightarrow kj$ := specific DONAU public key used 
to attribute a specific value to a DU, e.g. k1 gives the DU a value of 1, k2 a 
value of 2...
+\end{itemize}
+
+\subsection{Unique Donor ID (UDID)}
+
+The NONCE is used to uniquely distinguish donor IDs of the same value
+("create a fresh donor ID").  Otherwise the DONAU would refuse DUs
+containing donations of equal amount to the same charity, since this
+would be seen as "double spending" (or rather, double claiming of
+tax deduction for the same donation).
+
+\begin{align}
+  UDID := \langle H(TAXID, SALT), NONCE \rangle
+\end{align}
+
+\section{Overview}
+\includegraphics[width=\textwidth]{overview}
+
+\subsection{Step 0: Initial setup}
+\begin{enumerate}
+  \item Key generation for blind signatures and statement signing by the 
DONAU. Distribution of the keys to charities, donors and tax authorities 
(possibly on-demand via REST API). Let $ki$ be the private key for $i$ DU and 
$Pi$ be the corresponding public key.
+  \item The charity generates their own key pair (charity pub/priv).
+  \item The DONAU administrator registers the public key of the charity and 
sets the yearly donation limit for the charities.
+\end{enumerate}
+
+\subsection{Step 1: Attest donation}
+\subsubsection{Donor donates to charity}
+\begin{enumerate}
+  \item The donor downloads the DU public keys $P1, P4$ for the corresponding 
year from the DONAU.
+
+  \item To donate 5 Euros the donor has to generate 2 UDIDs (for 1 Euro and 4 
Euro DU).
+    The donor generates UDIDs $U1$ and $U2$ which include a salted hash of the 
tax number
+    (here TAXID) and a NONCE.
+
+  \begin{align}
+    U1 = \langle H(TAXID, SALT), NONCE_1 \rangle \\
+    U2 = \langle H(TAXID, SALT), NONCE_2 \rangle
+  \end{align}
+
+  \item The donor blinds the UDIDs using two different blinding factors $b_1, 
b_2$.
+  \begin{align}
+    BU1 = \langle blind(b_1,U1, P1), H(P1) \rangle \\
+    BU2 = \langle blind(b_2,U2, P4), H(P4) \rangle
+  \end{align}
+
+\item The donor sends the blinded UDIDs (BDIDs) $BU1$ and $BU2$ as well as the 
payment of 5 Euros.
+
+\end{enumerate}
+
+\subsubsection{Charity sends signed BDIDs to DONAU}
+\begin{enumerate}
+\item The charity verifies that the amount requested (based on the $H(Pi)$)
+      for signing is lower or equal to the effective amount of the donation.
+  \item The charity signs (using EdDSA) a structure containing all unsigned 
BDIDs coming from the donor.
+  \item The charity sends this structure and the signature to the DONAU.
+\end{enumerate}
+
+\subsubsection{DONAU sends back blind signed UDIDs to charity}
+\begin{enumerate}
+  \item The DONAU:
+    \begin{enumerate}
+      \item verifies the charity signature on the structure.
+      \item increments the current year amount of the charity by the total 
amount of the BDIDs, if the increment does not exceed the annual limit.
+      \item blind signs all the BDIDs using the private keys $k_i$ matching 
the public keys $H(Pi)$.
+        \begin{align}
+          BS1 &:= sign(BU1, k_1) \\
+          BS2 &:= sign(BU2, k_4)
+        \end{align}
+      \item sends back the blind signatures to the charity.
+    \end{enumerate}
+  \item The charity transmits the blind signatures to the donor.
+  \item The donor unblinds the signatures.
+  \begin{align}
+    S1_{k1} &= unblind(BS1, b_1) \\
+    S2_{k4} &= unblind(BS2, b_2)
+  \end{align}
+\end{enumerate}
+
+
+\subsection{Step 2: Donor sends DRs to DONAU, DONAU sends back donation 
statement (DS)}
+\begin{enumerate}
+  \item The donor sends the collection of all $\langle DUi, Si, H(Pj) 
\rangle$, also called DRs, to the DONAU. The DRs are sent manually once a year.
+  \item For each $\langle DUi, Si, H(Pj) \rangle$ The DONAU...
+
+  \begin{itemize}
+    \item check if $Pj$ is stored and get the corresponding year and donation 
unit (amount donated).
+    \item verifies if $Si$ is a correct signature with the corresponding 
public key $Pj$.
+    \item verifies that the hash of the TAXID and the salt is the same as in 
other DRs (With multiple wallets each wallet must simply obtain a separate DS!).
+    \item verifies that the nonce is different from each ever used nonce of 
this donor for the corresponding year.
+    \item if all of this is the case, it adds the amount corresponding to the 
public key to the total donation amount for the year.
+  \end{itemize}
+  \item The DONAU then signs over the total amount,
+  year and hashed TAXID+salt and sends signature and the total amount so far 
back to the donor.
+
+  \begin{align}
+    DS := sign(total amount, year, H(TAXID, salt))
+  \end{align}
+
+\end{enumerate}
+
+\subsection{Step 3: Donor sends QR Code to validator (tax office)}
+\begin{enumerate}
+  \item The donor generates a QR code containing the following and sends it to 
the validator/tax office:
+  \begin{itemize}
+    \item version of the protocol (one byte)
+    \item TAXID
+    \item salt
+    \item DS received from the DONAU
+    \item year
+    \item amount for the year
+  \end{itemize}
+
+\item The validator scans the QR code and validates that the signature 
corresponds to the current DONAU DS signing key.
+\end{enumerate}
+
+\end{document}

-- 
To stop receiving notification emails like this one, please contact
gnunet@gnunet.org.