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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).

Remark

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.

Requirements

See Wide Mouthed Frog.

References

[Low97]

Citations

[BAN89]: Michael Burrows, Martin Abadi, and Roger Needham. A logic of authentication. Technical Report 39, Digital Systems Research Center, february 1989.
[Low97]: 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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