src/HOL/Auth/Yahalom.thy
author paulson
Fri, 01 Nov 1996 18:34:34 +0100
changeset 2156 9c361df93bd5
parent 2125 92a08ee6a9cb
child 2284 80ebd1a213fd
permissions -rw-r--r--
Minor changes to comments
Ignore whitespace changes - Everywhere: Within whitespace: At end of lines:
1995
c80e58e78d9c Addition of Yahalom protocol
paulson
parents: 1985
diff changeset
     1
(*  Title:      HOL/Auth/Yahalom
1985
84cf16192e03 Tidied many proofs, using AddIffs to let equivalences take
paulson
parents:
diff changeset
     2
    ID:         $Id$
84cf16192e03 Tidied many proofs, using AddIffs to let equivalences take
paulson
parents:
diff changeset
     3
    Author:     Lawrence C Paulson, Cambridge University Computer Laboratory
84cf16192e03 Tidied many proofs, using AddIffs to let equivalences take
paulson
parents:
diff changeset
     4
    Copyright   1996  University of Cambridge
84cf16192e03 Tidied many proofs, using AddIffs to let equivalences take
paulson
parents:
diff changeset
     5
84cf16192e03 Tidied many proofs, using AddIffs to let equivalences take
paulson
parents:
diff changeset
     6
Inductive relation "yahalom" for the Yahalom protocol.
84cf16192e03 Tidied many proofs, using AddIffs to let equivalences take
paulson
parents:
diff changeset
     7
84cf16192e03 Tidied many proofs, using AddIffs to let equivalences take
paulson
parents:
diff changeset
     8
From page 257 of
84cf16192e03 Tidied many proofs, using AddIffs to let equivalences take
paulson
parents:
diff changeset
     9
  Burrows, Abadi and Needham.  A Logic of Authentication.
84cf16192e03 Tidied many proofs, using AddIffs to let equivalences take
paulson
parents:
diff changeset
    10
  Proc. Royal Soc. 426 (1989)
84cf16192e03 Tidied many proofs, using AddIffs to let equivalences take
paulson
parents:
diff changeset
    11
*)
84cf16192e03 Tidied many proofs, using AddIffs to let equivalences take
paulson
parents:
diff changeset
    12
1995
c80e58e78d9c Addition of Yahalom protocol
paulson
parents: 1985
diff changeset
    13
Yahalom = Shared + 
1985
84cf16192e03 Tidied many proofs, using AddIffs to let equivalences take
paulson
parents:
diff changeset
    14
2032
1bbf1bdcaf56 Introduction of "lost" argument
paulson
parents: 1995
diff changeset
    15
consts  yahalom   :: "agent set => event list set"
1bbf1bdcaf56 Introduction of "lost" argument
paulson
parents: 1995
diff changeset
    16
inductive "yahalom lost"
1985
84cf16192e03 Tidied many proofs, using AddIffs to let equivalences take
paulson
parents:
diff changeset
    17
  intrs 
84cf16192e03 Tidied many proofs, using AddIffs to let equivalences take
paulson
parents:
diff changeset
    18
         (*Initial trace is empty*)
2032
1bbf1bdcaf56 Introduction of "lost" argument
paulson
parents: 1995
diff changeset
    19
    Nil  "[]: yahalom lost"
1985
84cf16192e03 Tidied many proofs, using AddIffs to let equivalences take
paulson
parents:
diff changeset
    20
2032
1bbf1bdcaf56 Introduction of "lost" argument
paulson
parents: 1995
diff changeset
    21
         (*The spy MAY say anything he CAN say.  We do not expect him to
1985
84cf16192e03 Tidied many proofs, using AddIffs to let equivalences take
paulson
parents:
diff changeset
    22
           invent new nonces here, but he can also use NS1.  Common to
84cf16192e03 Tidied many proofs, using AddIffs to let equivalences take
paulson
parents:
diff changeset
    23
           all similar protocols.*)
2032
1bbf1bdcaf56 Introduction of "lost" argument
paulson
parents: 1995
diff changeset
    24
    Fake "[| evs: yahalom lost;  B ~= Spy;  
1bbf1bdcaf56 Introduction of "lost" argument
paulson
parents: 1995
diff changeset
    25
             X: synth (analz (sees lost Spy evs)) |]
1bbf1bdcaf56 Introduction of "lost" argument
paulson
parents: 1995
diff changeset
    26
          ==> Says Spy B X  # evs : yahalom lost"
1985
84cf16192e03 Tidied many proofs, using AddIffs to let equivalences take
paulson
parents:
diff changeset
    27
84cf16192e03 Tidied many proofs, using AddIffs to let equivalences take
paulson
parents:
diff changeset
    28
         (*Alice initiates a protocol run*)
2032
1bbf1bdcaf56 Introduction of "lost" argument
paulson
parents: 1995
diff changeset
    29
    YM1  "[| evs: yahalom lost;  A ~= B |]
1bbf1bdcaf56 Introduction of "lost" argument
paulson
parents: 1995
diff changeset
    30
          ==> Says A B {|Agent A, Nonce (newN evs)|} # evs : yahalom lost"
1985
84cf16192e03 Tidied many proofs, using AddIffs to let equivalences take
paulson
parents:
diff changeset
    31
84cf16192e03 Tidied many proofs, using AddIffs to let equivalences take
paulson
parents:
diff changeset
    32
         (*Bob's response to Alice's message.  Bob doesn't know who 
1995
c80e58e78d9c Addition of Yahalom protocol
paulson
parents: 1985
diff changeset
    33
	   the sender is, hence the A' in the sender field.*)
2032
1bbf1bdcaf56 Introduction of "lost" argument
paulson
parents: 1995
diff changeset
    34
    YM2  "[| evs: yahalom lost;  B ~= Server;
1995
c80e58e78d9c Addition of Yahalom protocol
paulson
parents: 1985
diff changeset
    35
             Says A' B {|Agent A, Nonce NA|} : set_of_list evs |]
1985
84cf16192e03 Tidied many proofs, using AddIffs to let equivalences take
paulson
parents:
diff changeset
    36
          ==> Says B Server 
84cf16192e03 Tidied many proofs, using AddIffs to let equivalences take
paulson
parents:
diff changeset
    37
                  {|Agent B, 
84cf16192e03 Tidied many proofs, using AddIffs to let equivalences take
paulson
parents:
diff changeset
    38
                    Crypt {|Agent A, Nonce NA, Nonce (newN evs)|} (shrK B)|}
2032
1bbf1bdcaf56 Introduction of "lost" argument
paulson
parents: 1995
diff changeset
    39
                 # evs : yahalom lost"
1985
84cf16192e03 Tidied many proofs, using AddIffs to let equivalences take
paulson
parents:
diff changeset
    40
84cf16192e03 Tidied many proofs, using AddIffs to let equivalences take
paulson
parents:
diff changeset
    41
         (*The Server receives Bob's message.  He responds by sending a
84cf16192e03 Tidied many proofs, using AddIffs to let equivalences take
paulson
parents:
diff changeset
    42
            new session key to Alice, with a packet for forwarding to Bob.*)
2032
1bbf1bdcaf56 Introduction of "lost" argument
paulson
parents: 1995
diff changeset
    43
    YM3  "[| evs: yahalom lost;  A ~= Server;
1985
84cf16192e03 Tidied many proofs, using AddIffs to let equivalences take
paulson
parents:
diff changeset
    44
             Says B' Server 
1995
c80e58e78d9c Addition of Yahalom protocol
paulson
parents: 1985
diff changeset
    45
                  {|Agent B, Crypt {|Agent A, Nonce NA, Nonce NB|} (shrK B)|}
1985
84cf16192e03 Tidied many proofs, using AddIffs to let equivalences take
paulson
parents:
diff changeset
    46
               : set_of_list evs |]
1995
c80e58e78d9c Addition of Yahalom protocol
paulson
parents: 1985
diff changeset
    47
          ==> Says Server A
c80e58e78d9c Addition of Yahalom protocol
paulson
parents: 1985
diff changeset
    48
                  {|Crypt {|Agent B, Key (newK evs), 
c80e58e78d9c Addition of Yahalom protocol
paulson
parents: 1985
diff changeset
    49
                            Nonce NA, Nonce NB|} (shrK A),
c80e58e78d9c Addition of Yahalom protocol
paulson
parents: 1985
diff changeset
    50
                    Crypt {|Agent A, Key (newK evs)|} (shrK B)|}
2032
1bbf1bdcaf56 Introduction of "lost" argument
paulson
parents: 1995
diff changeset
    51
                 # evs : yahalom lost"
1985
84cf16192e03 Tidied many proofs, using AddIffs to let equivalences take
paulson
parents:
diff changeset
    52
1995
c80e58e78d9c Addition of Yahalom protocol
paulson
parents: 1985
diff changeset
    53
         (*Alice receives the Server's (?) message, checks her Nonce, and
c80e58e78d9c Addition of Yahalom protocol
paulson
parents: 1985
diff changeset
    54
           uses the new session key to send Bob his Nonce.*)
2125
92a08ee6a9cb New Oops message, with Server as source to ensure
paulson
parents: 2110
diff changeset
    55
    YM4  "[| evs: yahalom lost;  A ~= Server;  A ~= B;  
1995
c80e58e78d9c Addition of Yahalom protocol
paulson
parents: 1985
diff changeset
    56
             Says S A {|Crypt {|Agent B, Key K, Nonce NA, Nonce NB|} (shrK A),
2125
92a08ee6a9cb New Oops message, with Server as source to ensure
paulson
parents: 2110
diff changeset
    57
                        X|}  : set_of_list evs;
1995
c80e58e78d9c Addition of Yahalom protocol
paulson
parents: 1985
diff changeset
    58
             Says A B {|Agent A, Nonce NA|} : set_of_list evs |]
2032
1bbf1bdcaf56 Introduction of "lost" argument
paulson
parents: 1995
diff changeset
    59
          ==> Says A B {|X, Crypt (Nonce NB) K|} # evs : yahalom lost"
1985
84cf16192e03 Tidied many proofs, using AddIffs to let equivalences take
paulson
parents:
diff changeset
    60
2110
d01151e66cd4 Addition of Reveal message
paulson
parents: 2032
diff changeset
    61
         (*This message models possible leaks of session keys.  The Nonces
2156
9c361df93bd5 Minor changes to comments
paulson
parents: 2125
diff changeset
    62
           identify the protocol run.  Quoting Server here ensures they are
9c361df93bd5 Minor changes to comments
paulson
parents: 2125
diff changeset
    63
           correct.*)
2125
92a08ee6a9cb New Oops message, with Server as source to ensure
paulson
parents: 2110
diff changeset
    64
    Oops "[| evs: yahalom lost;  A ~= Spy;
92a08ee6a9cb New Oops message, with Server as source to ensure
paulson
parents: 2110
diff changeset
    65
             Says Server A {|Crypt {|Agent B, Key K, Nonce NA, Nonce NB|} 
92a08ee6a9cb New Oops message, with Server as source to ensure
paulson
parents: 2110
diff changeset
    66
                                   (shrK A),
92a08ee6a9cb New Oops message, with Server as source to ensure
paulson
parents: 2110
diff changeset
    67
                             X|}  : set_of_list evs |]
2110
d01151e66cd4 Addition of Reveal message
paulson
parents: 2032
diff changeset
    68
          ==> Says A Spy {|Nonce NA, Nonce NB, Key K|} # evs : yahalom lost"
d01151e66cd4 Addition of Reveal message
paulson
parents: 2032
diff changeset
    69
1985
84cf16192e03 Tidied many proofs, using AddIffs to let equivalences take
paulson
parents:
diff changeset
    70
end