author | paulson |
Fri, 29 Nov 1996 18:03:21 +0100 | |
changeset 2284 | 80ebd1a213fd |
parent 2155 | dc85854810eb |
child 2378 | fc103154ad8f |
permissions | -rw-r--r-- |
2111
81c8d46edfa3
New version of Yahalom, as recommended on p 259 of BAN paper
paulson
parents:
diff
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1 |
(* Title: HOL/Auth/Yahalom |
81c8d46edfa3
New version of Yahalom, as recommended on p 259 of BAN paper
paulson
parents:
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2 |
ID: $Id$ |
81c8d46edfa3
New version of Yahalom, as recommended on p 259 of BAN paper
paulson
parents:
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|
3 |
Author: Lawrence C Paulson, Cambridge University Computer Laboratory |
81c8d46edfa3
New version of Yahalom, as recommended on p 259 of BAN paper
paulson
parents:
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4 |
Copyright 1996 University of Cambridge |
81c8d46edfa3
New version of Yahalom, as recommended on p 259 of BAN paper
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parents:
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5 |
|
81c8d46edfa3
New version of Yahalom, as recommended on p 259 of BAN paper
paulson
parents:
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6 |
Inductive relation "yahalom" for the Yahalom protocol, Variant 2. |
81c8d46edfa3
New version of Yahalom, as recommended on p 259 of BAN paper
paulson
parents:
diff
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7 |
|
81c8d46edfa3
New version of Yahalom, as recommended on p 259 of BAN paper
paulson
parents:
diff
changeset
|
8 |
This version trades encryption of NB for additional explicitness in YM3. |
2155 | 9 |
It also omits encryption in YM2. The resulting protocol no longer guarantees |
10 |
that the other agent is present. |
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2111
81c8d46edfa3
New version of Yahalom, as recommended on p 259 of BAN paper
paulson
parents:
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11 |
|
81c8d46edfa3
New version of Yahalom, as recommended on p 259 of BAN paper
paulson
parents:
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12 |
From page 259 of |
81c8d46edfa3
New version of Yahalom, as recommended on p 259 of BAN paper
paulson
parents:
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13 |
Burrows, Abadi and Needham. A Logic of Authentication. |
81c8d46edfa3
New version of Yahalom, as recommended on p 259 of BAN paper
paulson
parents:
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14 |
Proc. Royal Soc. 426 (1989) |
81c8d46edfa3
New version of Yahalom, as recommended on p 259 of BAN paper
paulson
parents:
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15 |
*) |
81c8d46edfa3
New version of Yahalom, as recommended on p 259 of BAN paper
paulson
parents:
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16 |
|
81c8d46edfa3
New version of Yahalom, as recommended on p 259 of BAN paper
paulson
parents:
diff
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17 |
Yahalom2 = Shared + |
81c8d46edfa3
New version of Yahalom, as recommended on p 259 of BAN paper
paulson
parents:
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18 |
|
81c8d46edfa3
New version of Yahalom, as recommended on p 259 of BAN paper
paulson
parents:
diff
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19 |
consts yahalom :: "agent set => event list set" |
81c8d46edfa3
New version of Yahalom, as recommended on p 259 of BAN paper
paulson
parents:
diff
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20 |
inductive "yahalom lost" |
81c8d46edfa3
New version of Yahalom, as recommended on p 259 of BAN paper
paulson
parents:
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21 |
intrs |
81c8d46edfa3
New version of Yahalom, as recommended on p 259 of BAN paper
paulson
parents:
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22 |
(*Initial trace is empty*) |
81c8d46edfa3
New version of Yahalom, as recommended on p 259 of BAN paper
paulson
parents:
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23 |
Nil "[]: yahalom lost" |
81c8d46edfa3
New version of Yahalom, as recommended on p 259 of BAN paper
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parents:
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24 |
|
81c8d46edfa3
New version of Yahalom, as recommended on p 259 of BAN paper
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parents:
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25 |
(*The spy MAY say anything he CAN say. We do not expect him to |
81c8d46edfa3
New version of Yahalom, as recommended on p 259 of BAN paper
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parents:
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26 |
invent new nonces here, but he can also use NS1. Common to |
81c8d46edfa3
New version of Yahalom, as recommended on p 259 of BAN paper
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parents:
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27 |
all similar protocols.*) |
81c8d46edfa3
New version of Yahalom, as recommended on p 259 of BAN paper
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parents:
diff
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28 |
Fake "[| evs: yahalom lost; B ~= Spy; |
81c8d46edfa3
New version of Yahalom, as recommended on p 259 of BAN paper
paulson
parents:
diff
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29 |
X: synth (analz (sees lost Spy evs)) |] |
81c8d46edfa3
New version of Yahalom, as recommended on p 259 of BAN paper
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parents:
diff
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30 |
==> Says Spy B X # evs : yahalom lost" |
81c8d46edfa3
New version of Yahalom, as recommended on p 259 of BAN paper
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parents:
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31 |
|
81c8d46edfa3
New version of Yahalom, as recommended on p 259 of BAN paper
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parents:
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32 |
(*Alice initiates a protocol run*) |
81c8d46edfa3
New version of Yahalom, as recommended on p 259 of BAN paper
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parents:
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33 |
YM1 "[| evs: yahalom lost; A ~= B |] |
81c8d46edfa3
New version of Yahalom, as recommended on p 259 of BAN paper
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parents:
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34 |
==> Says A B {|Agent A, Nonce (newN evs)|} # evs : yahalom lost" |
81c8d46edfa3
New version of Yahalom, as recommended on p 259 of BAN paper
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parents:
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35 |
|
81c8d46edfa3
New version of Yahalom, as recommended on p 259 of BAN paper
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parents:
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36 |
(*Bob's response to Alice's message. Bob doesn't know who |
81c8d46edfa3
New version of Yahalom, as recommended on p 259 of BAN paper
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parents:
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37 |
the sender is, hence the A' in the sender field.*) |
81c8d46edfa3
New version of Yahalom, as recommended on p 259 of BAN paper
paulson
parents:
diff
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38 |
YM2 "[| evs: yahalom lost; B ~= Server; |
81c8d46edfa3
New version of Yahalom, as recommended on p 259 of BAN paper
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parents:
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39 |
Says A' B {|Agent A, Nonce NA|} : set_of_list evs |] |
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==> Says B Server {|Agent A, Agent B, Nonce NA, Nonce (newN evs)|} |
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81c8d46edfa3
New version of Yahalom, as recommended on p 259 of BAN paper
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parents:
diff
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41 |
# evs : yahalom lost" |
81c8d46edfa3
New version of Yahalom, as recommended on p 259 of BAN paper
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parents:
diff
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42 |
|
81c8d46edfa3
New version of Yahalom, as recommended on p 259 of BAN paper
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parents:
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43 |
(*The Server receives Bob's message. He responds by sending a |
2155 | 44 |
new session key to Alice, with a packet for forwarding to Bob. |
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Fields are reversed in the 2nd packet to prevent attacks.*) |
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46 |
YM3 "[| evs: yahalom lost; A ~= B; A ~= Server; |
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Says B' Server {|Agent A, Agent B, Nonce NA, Nonce NB|} |
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2111
81c8d46edfa3
New version of Yahalom, as recommended on p 259 of BAN paper
paulson
parents:
diff
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48 |
: set_of_list evs |] |
81c8d46edfa3
New version of Yahalom, as recommended on p 259 of BAN paper
paulson
parents:
diff
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49 |
==> Says Server A |
81c8d46edfa3
New version of Yahalom, as recommended on p 259 of BAN paper
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parents:
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50 |
{|Nonce NB, |
2284
80ebd1a213fd
Swapped arguments of Crypt (for clarity and because it is conventional)
paulson
parents:
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51 |
Crypt (shrK A) {|Agent B, Key (newK evs), Nonce NA|}, |
80ebd1a213fd
Swapped arguments of Crypt (for clarity and because it is conventional)
paulson
parents:
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52 |
Crypt (shrK B) {|Nonce NB, Key (newK evs), Agent A|}|} |
2111
81c8d46edfa3
New version of Yahalom, as recommended on p 259 of BAN paper
paulson
parents:
diff
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53 |
# evs : yahalom lost" |
81c8d46edfa3
New version of Yahalom, as recommended on p 259 of BAN paper
paulson
parents:
diff
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54 |
|
81c8d46edfa3
New version of Yahalom, as recommended on p 259 of BAN paper
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parents:
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55 |
(*Alice receives the Server's (?) message, checks her Nonce, and |
81c8d46edfa3
New version of Yahalom, as recommended on p 259 of BAN paper
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parents:
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56 |
uses the new session key to send Bob his Nonce.*) |
2155 | 57 |
YM4 "[| evs: yahalom lost; A ~= Server; A ~= B; |
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80ebd1a213fd
Swapped arguments of Crypt (for clarity and because it is conventional)
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parents:
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58 |
Says S A {|Nonce NB, Crypt (shrK A) {|Agent B, Key K, Nonce NA|}, |
2111
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New version of Yahalom, as recommended on p 259 of BAN paper
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parents:
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59 |
X|} |
81c8d46edfa3
New version of Yahalom, as recommended on p 259 of BAN paper
paulson
parents:
diff
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60 |
: set_of_list evs; |
81c8d46edfa3
New version of Yahalom, as recommended on p 259 of BAN paper
paulson
parents:
diff
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61 |
Says A B {|Agent A, Nonce NA|} : set_of_list evs |] |
2284
80ebd1a213fd
Swapped arguments of Crypt (for clarity and because it is conventional)
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parents:
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62 |
==> Says A B {|X, Crypt K (Nonce NB)|} # evs : yahalom lost" |
2111
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New version of Yahalom, as recommended on p 259 of BAN paper
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parents:
diff
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63 |
|
2155 | 64 |
(*This message models possible leaks of session keys. The nonces |
65 |
identify the protocol run. Quoting Server here ensures they are |
|
66 |
correct. *) |
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67 |
Oops "[| evs: yahalom lost; A ~= Spy; |
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68 |
Says Server A {|Nonce NB, |
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2284
80ebd1a213fd
Swapped arguments of Crypt (for clarity and because it is conventional)
paulson
parents:
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69 |
Crypt (shrK A) {|Agent B, Key K, Nonce NA|}, |
2155 | 70 |
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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2111
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New version of Yahalom, as recommended on p 259 of BAN paper
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parents:
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72 |
|
81c8d46edfa3
New version of Yahalom, as recommended on p 259 of BAN paper
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parents:
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73 |
end |