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Lowe modified Wide Mouthed Frog

Author(s): Gavin Lowe  (1997)

Summary: An modified version of Wide Mouthed Frog. Exchanged of a fresh shared key. Symmetric key cryptography with server and timestamps.

Protocol specification (in common syntax)

A, S :   principal
Kas, Kbs, Kab :   symkey
Nb :   nonce
Ta, Ts :   timestamp
suc :   nonce -> nonce

1.   A -> S :   A, {Ta, B, Kab}Kas
2.   S -> B :   {Ts, A, Kab}Kbs
3.   B -> A :   {Nb}Kab
4.   A -> B :   {succ(Nb)}Kab

Description of the protocol rules

Two messages have been appened to Wide Mouthed Frog for mutual authentification of A and B (nonce handshake).


The two final messages were added by Lowe to the Wide Mouthed Frog protocol to prevent an attack claimed in [Low97] which actually fails against the complete original specification of the protocol in [BAN89], see Wide Mouthed Frog.


See Wide Mouthed Frog.



See also

Wide Mouthed Frog


Michael Burrows, Martin Abadi, and Roger Needham. A logic of authentication. Technical Report 39, Digital Systems Research Center, february 1989.

Gavin Lowe. A family of attacks upon authentication protocols. Technical Report 1997/5, Department of Mathematics and Computer Science, University of Leicester, 1997.
last modified 20/11/2002.
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