author | paulson |
Thu, 24 Oct 1996 10:38:35 +0200 | |
changeset 2125 | 92a08ee6a9cb |
parent 2110 | d01151e66cd4 |
child 2156 | 9c361df93bd5 |
permissions | -rw-r--r-- |
1995 | 1 |
(* Title: HOL/Auth/Yahalom |
1985
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ID: $Id$ |
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Author: Lawrence C Paulson, Cambridge University Computer Laboratory |
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Copyright 1996 University of Cambridge |
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Inductive relation "yahalom" for the Yahalom protocol. |
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From page 257 of |
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Burrows, Abadi and Needham. A Logic of Authentication. |
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Proc. Royal Soc. 426 (1989) |
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*) |
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Yahalom = Shared + |
1985
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consts yahalom :: "agent set => event list set" |
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inductive "yahalom lost" |
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1985
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intrs |
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(*Initial trace is empty*) |
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Nil "[]: yahalom lost" |
1985
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(*The spy MAY say anything he CAN say. We do not expect him to |
1985
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invent new nonces here, but he can also use NS1. Common to |
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all similar protocols.*) |
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Fake "[| evs: yahalom lost; B ~= Spy; |
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X: synth (analz (sees lost Spy evs)) |] |
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==> Says Spy B X # evs : yahalom lost" |
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1985
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(*Alice initiates a protocol run*) |
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YM1 "[| evs: yahalom lost; A ~= B |] |
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==> Says A B {|Agent A, Nonce (newN evs)|} # evs : yahalom lost" |
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1985
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(*Bob's response to Alice's message. Bob doesn't know who |
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the sender is, hence the A' in the sender field.*) |
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YM2 "[| evs: yahalom lost; B ~= Server; |
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Says A' B {|Agent A, Nonce NA|} : set_of_list evs |] |
1985
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==> Says B Server |
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{|Agent B, |
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Crypt {|Agent A, Nonce NA, Nonce (newN evs)|} (shrK B)|} |
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# evs : yahalom lost" |
1985
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(*The Server receives Bob's message. He responds by sending a |
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new session key to Alice, with a packet for forwarding to Bob.*) |
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YM3 "[| evs: yahalom lost; A ~= Server; |
1985
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Says B' Server |
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{|Agent B, Crypt {|Agent A, Nonce NA, Nonce NB|} (shrK B)|} |
1985
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: set_of_list evs |] |
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==> Says Server A |
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{|Crypt {|Agent B, Key (newK evs), |
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Nonce NA, Nonce NB|} (shrK A), |
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Crypt {|Agent A, Key (newK evs)|} (shrK B)|} |
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# evs : yahalom lost" |
1985
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(*Alice receives the Server's (?) message, checks her Nonce, and |
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uses the new session key to send Bob his Nonce.*) |
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YM4 "[| evs: yahalom lost; A ~= Server; A ~= B; |
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Says S A {|Crypt {|Agent B, Key K, Nonce NA, Nonce NB|} (shrK A), |
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X|} : set_of_list evs; |
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Says A B {|Agent A, Nonce NA|} : set_of_list evs |] |
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==> Says A B {|X, Crypt (Nonce NB) K|} # evs : yahalom lost" |
1985
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(*This message models possible leaks of session keys. The Nonces |
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identify the protocol run.*) |
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Oops "[| evs: yahalom lost; A ~= Spy; |
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Says Server A {|Crypt {|Agent B, Key K, Nonce NA, Nonce NB|} |
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(shrK A), |
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X|} : set_of_list evs |] |
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==> Says A Spy {|Nonce NA, Nonce NB, Key K|} # evs : yahalom lost" |
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1985
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end |