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Kao Chow Authentication v.2

Author(s): I Long Kao and Randy Chow  (1995)

Summary: Key distribution and authentication protocol. Symmetric keys cryptography with server.


This protocol is a correction of Kao Chow Authentication v.1 to prevent a freshness attack la Denning Sacco attack (see Needham Schroeder Symmetric Key).

Protocol specification (in common syntax)

A, B, S :   principal
Na, Nb :   number
Kab, Kbs, Kas :   key

1.   A -> S :   A, B, Na
2.   S -> B :   {A, B, Na, Kab, Kt}Kas, {A, B, Na, Kab, Kt}Kbs
3.   B -> A :   B, {A, B, Na, Kab, Kt}Kas, {Na, Kab}Kt, Nb
4.   A -> B :   {Nb, Kab}Kt

Description of the protocol rules

See Kao Chow Authentication v.1. Kt is an additional fresh symmetric key whose purpose is to prevent a freshness attack as in Kao Chow Authentication v.1.


See Kao Chow Authentication v.1.



This specification of the protocol differs from the one in [CJ97].

Claimed proofs


See also

Kao Chow Authentication v.1, Kao Chow Authentication v.3, Needham Schroeder Symmetric Key, Neumann Stubblebine.


John Clark and Jeremy Jacob. A survey of authentication protocol literature : Version 1.0., November 1997.

I Lung Kao and Randy Chow. An efficient and secure authentication protocol using uncertified keys. Operating Systems Review, 29(3):14--21, 1995.
last modified 11/11/2002.
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