% File              : ccittx509_3BAN.tex
% Version           : $Revision: 1.1 $
% Last-modified     : $Date: 2005/01/04 11:45:32 $
% Last-modifier     : FJ

\documentclass{splib}

\begin{document}
% main environment
\begin{protocol}%
% name
{BAN modified version of CCITT X.509 (3)}%
% authors
{Michael Burrows and Martin Abadi and Roger Needham}%
% date of the first publication
{1989}%
% editor name
{}%
% date of submission
{}%
% date of last change, empty or = date of submission
{16/01/2003}

\begin{abstract}
Modified version of the three messages protocol 
in the recommendations of the CCITT for the CCITT.X.509 standard
(\crossref{ccittx509_3}).
\end{abstract}

\begin{core}
\begin{declarations}
\dcl{A, B}{principal}
\dcl{Na, Nb}{nonce}
\dcl{Ya, Yb}{userdata}
\dcl{Xa, Xb}{userdata}
\dcl{PK, SK}{principal -> key (keypair)}
\end{declarations}

\begin{messages}
\msg{1}{A}{B}{A, \crypt{Na, B, Xa, \crypt{Ya}{PK(B)}}{SK(A)}}
\msg{2}{B}{A}{B, \crypt{Nb, A, Na, Xb, \crypt{Yb}{PK(A)}}{SK(B)}}
\msg{3}{A}{B}{A, \crypt{B, Nb}{SK(A)}}
\end{messages}
\end{core}

\begin{explanation}
Compared to \crossref{ccittx509_3}, the identity of \code{B} has been 
added to the signature in message \code{3}.
This prevents the \cite{BurrowsAbadiNeedham89} attack 
on the \crossref{ccittx509_3} protocol, which can occur
when \code{B} does not check the timestamps.
With this modification, the timestamps become redundant and
can be removed.
\end{explanation}

\begin{property}
See \crossref{ccittx509_3}.
\end{property}

\begin{references}
\cite{BurrowsAbadiNeedham89}.
\end{references}

\begin{see} %\crossref{}, see all.aux for labels names
\crossref{ccittx509_1},
\crossref{ccittx509_1c},
\crossref{ccittx509_3}.
\end{see}

\end{protocol}
\end{document}

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