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Update RedDSA verification to use cofactor multiplication. 

This is necessary in order for the output of batch verification to match unbatched verification in all cases.

Signed-off-by: Daira Hopwood <daira@jacaranda.org>
This commit is contained in:
Daira Hopwood 2018-07-27 21:31:20 +01:00
parent ea61325c25
commit 90692541aa
1 changed files with 13 additions and 1 deletions
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14
protocol/protocol.tex
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@ -6559,7 +6559,7 @@ Define $\RedDSAVerify{} \typecolon (\vk \typecolon \RedDSAPublic) \times (M \typ
\item Let $\vkBytes = \LEBStoOSPOf{\ellG{}}{\reprGOf{}{\vk}}$.
\item Let $\RedDSASigc = \RedDSAHashToScalar(\RedDSAReprR \bconcat \vkBytes \bconcat M)$.
\item Return $1$ if $\RedDSASigR \neq \bot$ and $\RedDSASigS < \ParamG{r}$ and
$\scalarmult{\RedDSASigS}{\GenG{}} = \RedDSASigR + \scalarmult{\RedDSASigc}{\vk}$, otherwise $0$.
$\scalarmult{\ParamG{h}}{\big(\!\!-\scalarmult{\RedDSASigS}{\GenG{}} + \RedDSASigR + \scalarmult{\RedDSASigc}{\vk}\big)} = \ZeroG{}$, otherwise $0$.
\end{algorithm}
\vspace{-4ex}
@ -9553,6 +9553,18 @@ Peter Newell's illustration of the Jubjub bird, from \cite{Carroll1902}.
\intropart
\section{Change History}
\subparagraph{2018.0-beta-23}
\begin{itemize}
\item No changes to \Sprout.
\sapling{
\item Update $\RedDSA$ verification to use cofactor multiplication.
This is necessary in order for the output of batch verification to match
that of unbatched verification in all cases.
} %sapling
\end{itemize}
\introlist
\subparagraph{2018.0-beta-22}
\begin{itemize}