% File              : kslLowe.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
{Lowe modified KSL}%
% authors
{Gavin Lowe}%
% date of the first publication
{1996}%
% editor name
{}
% submission date
{}
% date of last change, empty or = date of submission
{02/12/2002}

\begin{abstract}
Lowe modified version of the \crossref{ksl} protocol
to prevent authentication attacks.
Distribution of a session key and a ticket and 
repeated mutual authentication.
Symmetric key cryptography with server.
\end{abstract}

\begin{core}
\begin{declarations}
\dcl{A, B, S}{principal}
\dcl{Na, Nb, Nc, Ma, Mb}{number}
\dcl{Kas, Kbs, Kab, Kbb}{key}
\dcl{Tb}{generalizedTimestamp}
\end{declarations}

\begin{messages}
\msg{1}{A}{B}{Na, A}
\msg{2}{B}{S}{Na, A, Nb, B}
\msg{3}{S}{B}{\crypt{A, Nb Kab}{Kbs}, \crypt{Na, B, Kab}{Kas}}
\msg{4}{B}{A}{\crypt{Na, B, Kab}{Kas}, \crypt{Tb, A, Kab}{Kbb}, Nc, \crypt{B, Na}{Kab}}
\msg{5}{A}{B}{\crypt{Nc}{Kab}}
\msg{}{}{}{}
\msg{6}{A}{B}{Ma, \crypt{Tb, A, Kab}{Kbb}}
\msg{7}{B}{A}{Mb, \crypt{Ma, B}{Kab}}
\msg{8}{A}{B}{\crypt{A, Mb}{Kab}}
\end{messages}
\end{core}

\begin{explanation}
See \crossref{ksl}.

The version given above has been devised from the following modifications
to \crossref{ksl} advised in~\cite{Lowe96}:
\begin{itemize}
\item ``change the message \code{3} so that the 
two encrypted components have different forms'' (in order to break symmetry),
\item ``make the encrypted components in \code{4}, \code{7} and \code{8}
  different'',
\item ``include either \code{A}'s or \code{B}'s identity in these last
  three components''.
\end{itemize}
\end{explanation}

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

\begin{references}
\cite{Lowe96}
\end{references}

\begin{see}
\crossref{ksl}
\end{see}
\end{protocol}
\end{document}

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