commit b829609bca943864c665839b627a51c2aeee994f
parent 2477aa0efa1add2a3ecd2a537c947569a13f0468
Author: Matyja Lukas Adam <lukas.matyja@students.bfh.ch>
Date: Sat, 30 Sep 2023 19:35:50 +0200
multiple upload of donation receipts during a year, remove text fields from image, other adjustments
Diffstat:
2 files changed, 14 insertions(+), 11 deletions(-)
diff --git a/doc/flows/images/overview.png b/doc/flows/images/overview.png
Binary files differ.
diff --git a/doc/flows/main.tex b/doc/flows/main.tex
@@ -22,6 +22,7 @@
\section{Definitions}
\begin{itemize}
\item $m :=$ \textbf{receipt} = smallest structure representing a donation confirmation unit, e.g. receipt for CHF1, CHF2. Equivalent in Taler is "coin".
+ \item BDR := blinded donation receipt (collection of blinded receipts)
\item $b :=$ Blinding factor
\item $H :=$ Cryptographic hash function
\item $statement_{year} :=$ sum of donations (receipts) for one specific year and specific donor
@@ -47,7 +48,7 @@ The NONCE is used to uniquely distinguish receipts of the same value ("create a
\subsection{Step 0: Initial setup}
\begin{enumerate}
\item The charity generates their own key pair.
- \item The DONAU administrator registers the public key of the charity and sets the yearly donation limit.
+ \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: Donor donates to charity}
@@ -61,8 +62,7 @@ The NONCE is used to uniquely distinguish receipts of the same value ("create a
m2 = \langle H(TAXID, SALT), NONCE_2 \rangle
\end{align}
- \item The donor blinds the receipts using two different blinding factors $b_1, b_2$ and sends them as $m1'$ and $m2'$ to the charity in addition to the payment of 3 Euros.
-
+ \item The donor blinds the receipts using two different blinding factors $b_1, b_2$.
\begin{align}
m1' = m1 \cdot b_1^{e_{1EUR}} \mod n_{1EUR} \\
m2' = m2 \cdot b_2^{e_{4EUR}} \mod n_{4EUR}
@@ -73,13 +73,15 @@ The NONCE is used to uniquely distinguish receipts of the same value ("create a
m1'_{k1} = sign_{k1}(m1') \\
m2'_{k4} = sign_{k4}(m2')
\end{align}
+
+ \item The donor sends the blinded receipts (BDR) $m1'$ and $m2'$ as well as the signatures $m1'$ and $m2'$ to the charity in addition to the payment of 3 Euros.
\end{enumerate}
\subsection{Step 2: Charity sends signed receipt to DONAU}
\begin{enumerate}
\item The charity verifies that the amount requested for signing is lower or equal to the effective amount of the donation.
\item The charity signs(EdDSA, more efficient than RSA-based signatures) a structure containing all unsigned receipts coming from the donor.
- \item The charity sends this structure to the DONAU.
+ \item The charity sends this structure and the signature to the DONAU.
\end{enumerate}
\subsection{Step 3: DONAU sends back blind signed receipt to charity}
@@ -88,7 +90,7 @@ The NONCE is used to uniquely distinguish receipts of the same value ("create a
\begin{enumerate}
\item verifies the charity Signature on the structure.
\item verifies the signature of every receipt with it's private keys.
- \item increments the current year amount of the charity by the total amount of the receipts.
+ \item increments the current year amount of the charity by the total amount of the receipts, if the increment does not exceed the annual limit.
\item blind signs (RSA/Schnorr) all the receipts
\end{enumerate}
\begin{align}
@@ -106,18 +108,18 @@ The NONCE is used to uniquely distinguish receipts of the same value ("create a
\subsection{Step 4: Donor sends receipts to DONAU, DONAU sends back statement}
\begin{enumerate}
- \item The donor sends the collection of all $(mi, si, kj)$ of the year to the DONAU.
+ \item The donor sends the collection of all $(mi, si, kj)$ to the DONAU. The donation receipts are always sent to the DONAU right after the donor has unblinded the receipts. The corresponding year is sent with.
\item For each $(mi, si, kj)$ The DONAU...
\begin{itemize}
- \item verifies that $kj$ is one of it's currently valid public keys
+ \item verifies that $kj$ is one of the valid public keys corresponding to the year indicated.
\item verifies if $si$ is a correct signature with the corresponding secret key.
- \item verifies that the hash of the TAXID and the salt is the same as in other receipts
- \item verifies that the nonce is different from the ones in other receipts
+ \item verifies that the hash of the TAXID and the salt is the same as in other receipts (how to solve the problem with multiple wallets?)
+ \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 amount, year and hashed TAXID+salt and sends signature back to the donor
+ \item The DONAU then signs over the amount, year and hashed TAXID+salt and sends signature and the total amount so far back to the donor.
\begin{align}
sign(total amount, year, hash(TAXID, salt))
@@ -134,9 +136,10 @@ The NONCE is used to uniquely distinguish receipts of the same value ("create a
\item signature received from the DONAU
\item year
\item amount for the year
+ \item version of the protocol(one byte)
\end{itemize}
- \item The validator scans the QR code. The app validates that the signature corresponds to the current DONAU statement signing key.
+ \item The validator scans the QR code and validates that the signature corresponds to the current DONAU statement signing key.
\end{enumerate}
\end{document}
