author | paulson |
Fri, 02 Jan 1998 17:15:19 +0100 | |
changeset 4509 | 828148415197 |
parent 4477 | b3e5857d8d99 |
child 4537 | 4e835bd9fada |
permissions | -rw-r--r-- |
1941 | 1 |
(* Title: HOL/Auth/OtwayRees |
2 |
ID: $Id$ |
|
3 |
Author: Lawrence C Paulson, Cambridge University Computer Laboratory |
|
4 |
Copyright 1996 University of Cambridge |
|
5 |
||
6 |
Inductive relation "otway" for the Otway-Rees protocol. |
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7 |
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Version that encrypts Nonce NB |
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|
1941 | 10 |
From page 244 of |
11 |
Burrows, Abadi and Needham. A Logic of Authentication. |
|
12 |
Proc. Royal Soc. 426 (1989) |
|
13 |
*) |
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14 |
||
15 |
open OtwayRees; |
|
16 |
||
4449 | 17 |
set proof_timing; |
1941 | 18 |
HOL_quantifiers := false; |
19 |
||
4470 | 20 |
AddEs spies_partsEs; |
21 |
AddDs [impOfSubs analz_subset_parts]; |
|
22 |
AddDs [impOfSubs Fake_parts_insert]; |
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23 |
||
1996
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24 |
|
2328 | 25 |
(*A "possibility property": there are traces that reach the end*) |
1996
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goal thy |
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"!!A B. [| A ~= B; A ~= Server; B ~= Server |] \ |
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\ ==> EX K. EX NA. EX evs: otway. \ |
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\ Says B A {|Nonce NA, Crypt (shrK A) {|Nonce NA, Key K|}|} \ |
3465 | 30 |
\ : set evs"; |
1996
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31 |
by (REPEAT (resolve_tac [exI,bexI] 1)); |
2032 | 32 |
by (rtac (otway.Nil RS otway.OR1 RS otway.OR2 RS otway.OR3 RS otway.OR4) 2); |
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by possibility_tac; |
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result(); |
1996
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35 |
|
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|
1941 | 37 |
(**** Inductive proofs about otway ****) |
38 |
||
39 |
(*Nobody sends themselves messages*) |
|
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goal thy "!!evs. evs : otway ==> ALL A X. Says A A X ~: set evs"; |
2032 | 41 |
by (etac otway.induct 1); |
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by Auto_tac; |
1941 | 43 |
qed_spec_mp "not_Says_to_self"; |
44 |
Addsimps [not_Says_to_self]; |
|
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AddSEs [not_Says_to_self RSN (2, rev_notE)]; |
|
46 |
||
47 |
||
48 |
(** For reasoning about the encrypted portion of messages **) |
|
49 |
||
3465 | 50 |
goal thy "!!evs. Says A' B {|N, Agent A, Agent B, X|} : set evs \ |
3683 | 51 |
\ ==> X : analz (spies evs)"; |
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52 |
by (dtac (Says_imp_spies RS analz.Inj) 1); |
4470 | 53 |
by (Blast_tac 1); |
3683 | 54 |
qed "OR2_analz_spies"; |
1941 | 55 |
|
3465 | 56 |
goal thy "!!evs. Says S' B {|N, X, Crypt (shrK B) X'|} : set evs \ |
3683 | 57 |
\ ==> X : analz (spies evs)"; |
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by (dtac (Says_imp_spies RS analz.Inj) 1); |
4470 | 59 |
by (Blast_tac 1); |
3683 | 60 |
qed "OR4_analz_spies"; |
1941 | 61 |
|
3465 | 62 |
goal thy "!!evs. Says Server B {|NA, X, Crypt K' {|NB,K|}|} : set evs \ |
3683 | 63 |
\ ==> K : parts (spies evs)"; |
4470 | 64 |
by (Blast_tac 1); |
3683 | 65 |
qed "Oops_parts_spies"; |
1941 | 66 |
|
67 |
(*OR2_analz... and OR4_analz... let us treat those cases using the same |
|
1964 | 68 |
argument as for the Fake case. This is possible for most, but not all, |
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proofs: Fake does not invent new nonces (as in OR2), and of course Fake |
|
2032 | 70 |
messages originate from the Spy. *) |
1964 | 71 |
|
3683 | 72 |
bind_thm ("OR2_parts_spies", |
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OR2_analz_spies RS (impOfSubs analz_subset_parts)); |
|
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bind_thm ("OR4_parts_spies", |
|
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OR4_analz_spies RS (impOfSubs analz_subset_parts)); |
|
2032 | 76 |
|
3683 | 77 |
(*For proving the easier theorems about X ~: parts (spies evs).*) |
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78 |
fun parts_induct_tac i = |
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79 |
etac otway.induct i THEN |
3683 | 80 |
forward_tac [Oops_parts_spies] (i+6) THEN |
81 |
forward_tac [OR4_parts_spies] (i+5) THEN |
|
82 |
forward_tac [OR2_parts_spies] (i+3) THEN |
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83 |
prove_simple_subgoals_tac i; |
1941 | 84 |
|
85 |
||
3683 | 86 |
(** Theorems of the form X ~: parts (spies evs) imply that NOBODY |
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sends messages containing X! **) |
1941 | 88 |
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89 |
|
3683 | 90 |
(*Spy never sees another agent's shared key! (unless it's bad at start)*) |
1941 | 91 |
goal thy |
3683 | 92 |
"!!evs. evs : otway ==> (Key (shrK A) : parts (spies evs)) = (A : bad)"; |
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93 |
by (parts_induct_tac 1); |
3961 | 94 |
by (ALLGOALS Blast_tac); |
2135 | 95 |
qed "Spy_see_shrK"; |
96 |
Addsimps [Spy_see_shrK]; |
|
1941 | 97 |
|
2135 | 98 |
goal thy |
3683 | 99 |
"!!evs. evs : otway ==> (Key (shrK A) : analz (spies evs)) = (A : bad)"; |
4091 | 100 |
by (auto_tac(claset() addDs [impOfSubs analz_subset_parts], simpset())); |
2135 | 101 |
qed "Spy_analz_shrK"; |
102 |
Addsimps [Spy_analz_shrK]; |
|
1941 | 103 |
|
4470 | 104 |
AddSDs [Spy_see_shrK RSN (2, rev_iffD1), |
105 |
Spy_analz_shrK RSN (2, rev_iffD1)]; |
|
1941 | 106 |
|
107 |
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108 |
(*Nobody can have used non-existent keys!*) |
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109 |
goal thy "!!evs. evs : otway ==> \ |
3683 | 110 |
\ Key K ~: used evs --> K ~: keysFor (parts (spies evs))"; |
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111 |
by (parts_induct_tac 1); |
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112 |
(*Fake*) |
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by (blast_tac (claset() addSDs [keysFor_parts_insert]) 1); |
3102 | 114 |
by (ALLGOALS Blast_tac); |
2160 | 115 |
qed_spec_mp "new_keys_not_used"; |
1941 | 116 |
|
117 |
bind_thm ("new_keys_not_analzd", |
|
2032 | 118 |
[analz_subset_parts RS keysFor_mono, |
119 |
new_keys_not_used] MRS contra_subsetD); |
|
1941 | 120 |
|
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Addsimps [new_keys_not_used, new_keys_not_analzd]; |
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122 |
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123 |
||
2064 | 124 |
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(*** Proofs involving analz ***) |
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126 |
||
2135 | 127 |
(*Describes the form of K and NA when the Server sends this message. Also |
128 |
for Oops case.*) |
|
2064 | 129 |
goal thy |
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"!!evs. [| Says Server B {|NA, X, Crypt (shrK B) {|NB, Key K|}|} : set evs; \ |
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\ evs : otway |] \ |
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132 |
\ ==> K ~: range shrK & (EX i. NA = Nonce i) & (EX j. NB = Nonce j)"; |
2135 | 133 |
by (etac rev_mp 1); |
134 |
by (etac otway.induct 1); |
|
3102 | 135 |
by (ALLGOALS Simp_tac); |
136 |
by (ALLGOALS Blast_tac); |
|
2135 | 137 |
qed "Says_Server_message_form"; |
2064 | 138 |
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139 |
||
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140 |
(*For proofs involving analz.*) |
3683 | 141 |
val analz_spies_tac = |
142 |
dtac OR2_analz_spies 4 THEN |
|
143 |
dtac OR4_analz_spies 6 THEN |
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forward_tac [Says_Server_message_form] 7 THEN |
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145 |
assume_tac 7 THEN |
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146 |
REPEAT ((eresolve_tac [exE, conjE] ORELSE' hyp_subst_tac) 7); |
1941 | 147 |
|
148 |
||
149 |
(**** |
|
150 |
The following is to prove theorems of the form |
|
151 |
||
3683 | 152 |
Key K : analz (insert (Key KAB) (spies evs)) ==> |
153 |
Key K : analz (spies evs) |
|
1941 | 154 |
|
155 |
A more general formula must be proved inductively. |
|
156 |
****) |
|
157 |
||
158 |
||
159 |
(** Session keys are not used to encrypt other session keys **) |
|
160 |
||
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161 |
(*The equality makes the induction hypothesis easier to apply*) |
1941 | 162 |
goal thy |
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163 |
"!!evs. evs : otway ==> \ |
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164 |
\ ALL K KK. KK <= Compl (range shrK) --> \ |
3683 | 165 |
\ (Key K : analz (Key``KK Un (spies evs))) = \ |
166 |
\ (K : KK | Key K : analz (spies evs))"; |
|
2032 | 167 |
by (etac otway.induct 1); |
3683 | 168 |
by analz_spies_tac; |
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169 |
by (REPEAT_FIRST (resolve_tac [allI, impI])); |
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170 |
by (REPEAT_FIRST (rtac analz_image_freshK_lemma )); |
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171 |
by (ALLGOALS (asm_simp_tac analz_image_freshK_ss)); |
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172 |
(*Fake*) |
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173 |
by (spy_analz_tac 1); |
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174 |
qed_spec_mp "analz_image_freshK"; |
1941 | 175 |
|
176 |
||
177 |
goal thy |
|
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178 |
"!!evs. [| evs : otway; KAB ~: range shrK |] ==> \ |
3683 | 179 |
\ Key K : analz (insert (Key KAB) (spies evs)) = \ |
180 |
\ (K = KAB | Key K : analz (spies evs))"; |
|
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181 |
by (asm_simp_tac (analz_image_freshK_ss addsimps [analz_image_freshK]) 1); |
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182 |
qed "analz_insert_freshK"; |
1941 | 183 |
|
184 |
||
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185 |
(*** The Key K uniquely identifies the Server's message. **) |
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186 |
|
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187 |
goal thy |
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188 |
"!!evs. evs : otway ==> \ |
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189 |
\ EX B' NA' NB' X'. ALL B NA NB X. \ |
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190 |
\ Says Server B {|NA, X, Crypt (shrK B) {|NB, K|}|} : set evs --> \ |
2135 | 191 |
\ B=B' & NA=NA' & NB=NB' & X=X'"; |
2032 | 192 |
by (etac otway.induct 1); |
4091 | 193 |
by (ALLGOALS (asm_simp_tac (simpset() addsimps [all_conj_distrib]))); |
3730 | 194 |
by (ALLGOALS Clarify_tac); |
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195 |
(*Remaining cases: OR3 and OR4*) |
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196 |
by (ex_strip_tac 2); |
3102 | 197 |
by (Best_tac 2); |
2064 | 198 |
by (expand_case_tac "K = ?y" 1); |
199 |
by (REPEAT (ares_tac [refl,exI,impI,conjI] 2)); |
|
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200 |
(*...we assume X is a recent message, and handle this case by contradiction*) |
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201 |
by (blast_tac (claset() addSEs spies_partsEs) 1); |
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202 |
val lemma = result(); |
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203 |
|
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204 |
goal thy |
3543 | 205 |
"!!evs. [| Says Server B {|NA, X, Crypt (shrK B) {|NB, K|}|} : set evs; \ |
206 |
\ Says Server B' {|NA',X',Crypt (shrK B') {|NB',K|}|} : set evs; \ |
|
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207 |
\ evs : otway |] ==> X=X' & B=B' & NA=NA' & NB=NB'"; |
2417 | 208 |
by (prove_unique_tac lemma 1); |
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209 |
qed "unique_session_keys"; |
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210 |
|
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211 |
|
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212 |
|
2048 | 213 |
(**** Authenticity properties relating to NA ****) |
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214 |
|
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215 |
(*Only OR1 can have caused such a part of a message to appear.*) |
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216 |
goal thy |
3683 | 217 |
"!!evs. [| A ~: bad; evs : otway |] \ |
218 |
\ ==> Crypt (shrK A) {|NA, Agent A, Agent B|} : parts (spies evs) --> \ |
|
2064 | 219 |
\ Says A B {|NA, Agent A, Agent B, \ |
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220 |
\ Crypt (shrK A) {|NA, Agent A, Agent B|}|} \ |
3465 | 221 |
\ : set evs"; |
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222 |
by (parts_induct_tac 1); |
4470 | 223 |
by (Blast_tac 1); |
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|
224 |
qed_spec_mp "Crypt_imp_OR1"; |
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|
225 |
|
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|
226 |
|
2064 | 227 |
(** The Nonce NA uniquely identifies A's message. **) |
2014
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|
228 |
|
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|
229 |
goal thy |
3683 | 230 |
"!!evs. [| evs : otway; A ~: bad |] \ |
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Changing "lost" from a parameter of protocol definitions to a constant.
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|
231 |
\ ==> EX B'. ALL B. \ |
3683 | 232 |
\ Crypt (shrK A) {|NA, Agent A, Agent B|} : parts (spies evs) \ |
2048 | 233 |
\ --> B = B'"; |
3519
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Changing "lost" from a parameter of protocol definitions to a constant.
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diff
changeset
|
234 |
by (parts_induct_tac 1); |
4470 | 235 |
by (Blast_tac 1); |
4091 | 236 |
by (simp_tac (simpset() addsimps [all_conj_distrib]) 1); |
2026
0df5a96bf77e
Last working version prior to introduction of "lost"
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2014
diff
changeset
|
237 |
(*OR1: creation of new Nonce. Move assertion into global context*) |
2064 | 238 |
by (expand_case_tac "NA = ?y" 1); |
4470 | 239 |
by (Blast_tac 1); |
2014
5be4c8ca7b25
Correction of protocol; addition of Reveal message; proofs of
paulson
parents:
1999
diff
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|
240 |
val lemma = result(); |
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Correction of protocol; addition of Reveal message; proofs of
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1999
diff
changeset
|
241 |
|
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parents:
1999
diff
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|
242 |
goal thy |
3683 | 243 |
"!!evs.[| Crypt (shrK A) {|NA, Agent A, Agent B|}: parts (spies evs); \ |
244 |
\ Crypt (shrK A) {|NA, Agent A, Agent C|}: parts (spies evs); \ |
|
245 |
\ evs : otway; A ~: bad |] \ |
|
2014
5be4c8ca7b25
Correction of protocol; addition of Reveal message; proofs of
paulson
parents:
1999
diff
changeset
|
246 |
\ ==> B = C"; |
2417 | 247 |
by (prove_unique_tac lemma 1); |
2048 | 248 |
qed "unique_NA"; |
2014
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Correction of protocol; addition of Reveal message; proofs of
paulson
parents:
1999
diff
changeset
|
249 |
|
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paulson
parents:
1999
diff
changeset
|
250 |
|
5be4c8ca7b25
Correction of protocol; addition of Reveal message; proofs of
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parents:
1999
diff
changeset
|
251 |
(*It is impossible to re-use a nonce in both OR1 and OR2. This holds because |
5be4c8ca7b25
Correction of protocol; addition of Reveal message; proofs of
paulson
parents:
1999
diff
changeset
|
252 |
OR2 encrypts Nonce NB. It prevents the attack that can occur in the |
5be4c8ca7b25
Correction of protocol; addition of Reveal message; proofs of
paulson
parents:
1999
diff
changeset
|
253 |
over-simplified version of this protocol: see OtwayRees_Bad.*) |
5be4c8ca7b25
Correction of protocol; addition of Reveal message; proofs of
paulson
parents:
1999
diff
changeset
|
254 |
goal thy |
3683 | 255 |
"!!evs. [| A ~: bad; evs : otway |] \ |
256 |
\ ==> Crypt (shrK A) {|NA, Agent A, Agent B|} : parts (spies evs) --> \ |
|
3519
ab0a9fbed4c0
Changing "lost" from a parameter of protocol definitions to a constant.
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parents:
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diff
changeset
|
257 |
\ Crypt (shrK A) {|NA', NA, Agent A', Agent A|} \ |
3683 | 258 |
\ ~: parts (spies evs)"; |
3519
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Changing "lost" from a parameter of protocol definitions to a constant.
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parents:
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diff
changeset
|
259 |
by (parts_induct_tac 1); |
4470 | 260 |
by (ALLGOALS Blast_tac); |
2014
5be4c8ca7b25
Correction of protocol; addition of Reveal message; proofs of
paulson
parents:
1999
diff
changeset
|
261 |
qed_spec_mp"no_nonce_OR1_OR2"; |
5be4c8ca7b25
Correction of protocol; addition of Reveal message; proofs of
paulson
parents:
1999
diff
changeset
|
262 |
|
4470 | 263 |
val nonce_OR1_OR2_E = no_nonce_OR1_OR2 RSN (2, rev_notE); |
2014
5be4c8ca7b25
Correction of protocol; addition of Reveal message; proofs of
paulson
parents:
1999
diff
changeset
|
264 |
|
2053 | 265 |
(*Crucial property: If the encrypted message appears, and A has used NA |
266 |
to start a run, then it originated with the Server!*) |
|
2014
5be4c8ca7b25
Correction of protocol; addition of Reveal message; proofs of
paulson
parents:
1999
diff
changeset
|
267 |
goal thy |
3683 | 268 |
"!!evs. [| A ~: bad; A ~= Spy; evs : otway |] \ |
269 |
\ ==> Crypt (shrK A) {|NA, Key K|} : parts (spies evs) \ |
|
2048 | 270 |
\ --> Says A B {|NA, Agent A, Agent B, \ |
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80ebd1a213fd
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diff
changeset
|
271 |
\ Crypt (shrK A) {|NA, Agent A, Agent B|}|} \ |
3466
30791e5a69c4
Corrected indentations and margins after the renaming of "set_of_list"
paulson
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diff
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|
272 |
\ : set evs --> \ |
2048 | 273 |
\ (EX NB. Says Server B \ |
274 |
\ {|NA, \ |
|
2284
80ebd1a213fd
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parents:
2264
diff
changeset
|
275 |
\ Crypt (shrK A) {|NA, Key K|}, \ |
80ebd1a213fd
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diff
changeset
|
276 |
\ Crypt (shrK B) {|NB, Key K|}|} \ |
3465 | 277 |
\ : set evs)"; |
3519
ab0a9fbed4c0
Changing "lost" from a parameter of protocol definitions to a constant.
paulson
parents:
3516
diff
changeset
|
278 |
by (parts_induct_tac 1); |
4470 | 279 |
by (Blast_tac 1); |
2014
5be4c8ca7b25
Correction of protocol; addition of Reveal message; proofs of
paulson
parents:
1999
diff
changeset
|
280 |
(*OR1: it cannot be a new Nonce, contradiction.*) |
4470 | 281 |
by (Blast_tac 1); |
3730 | 282 |
(*OR3 and OR4*) |
4091 | 283 |
by (asm_simp_tac (simpset() addsimps [ex_disj_distrib]) 1); |
3730 | 284 |
by (rtac conjI 1); |
285 |
by (ALLGOALS Clarify_tac); |
|
286 |
(*OR4*) |
|
4470 | 287 |
by (blast_tac (claset() addSIs [Crypt_imp_OR1]) 3); |
288 |
(*OR3, two cases*) (** LEVEL 7 **) |
|
289 |
by (blast_tac (claset() addSEs [nonce_OR1_OR2_E] |
|
290 |
delrules [conjI] (*stop split-up into 4 subgoals*)) 2); |
|
291 |
by (blast_tac (claset() addIs [unique_NA]) 1); |
|
2048 | 292 |
qed_spec_mp "NA_Crypt_imp_Server_msg"; |
2014
5be4c8ca7b25
Correction of protocol; addition of Reveal message; proofs of
paulson
parents:
1999
diff
changeset
|
293 |
|
5be4c8ca7b25
Correction of protocol; addition of Reveal message; proofs of
paulson
parents:
1999
diff
changeset
|
294 |
|
2053 | 295 |
(*Corollary: if A receives B's OR4 message and the nonce NA agrees |
2014
5be4c8ca7b25
Correction of protocol; addition of Reveal message; proofs of
paulson
parents:
1999
diff
changeset
|
296 |
then the key really did come from the Server! CANNOT prove this of the |
2048 | 297 |
bad form of this protocol, even though we can prove |
2032 | 298 |
Spy_not_see_encrypted_key*) |
2014
5be4c8ca7b25
Correction of protocol; addition of Reveal message; proofs of
paulson
parents:
1999
diff
changeset
|
299 |
goal thy |
3683 | 300 |
"!!evs. [| Says B' A {|NA, Crypt (shrK A) {|NA, Key K|}|} : set evs; \ |
301 |
\ Says A B {|NA, Agent A, Agent B, \ |
|
302 |
\ Crypt (shrK A) {|NA, Agent A, Agent B|}|} : set evs; \ |
|
303 |
\ A ~: bad; A ~= Spy; evs : otway |] \ |
|
2053 | 304 |
\ ==> EX NB. Says Server B \ |
2048 | 305 |
\ {|NA, \ |
2284
80ebd1a213fd
Swapped arguments of Crypt (for clarity and because it is conventional)
paulson
parents:
2264
diff
changeset
|
306 |
\ Crypt (shrK A) {|NA, Key K|}, \ |
80ebd1a213fd
Swapped arguments of Crypt (for clarity and because it is conventional)
paulson
parents:
2264
diff
changeset
|
307 |
\ Crypt (shrK B) {|NB, Key K|}|} \ |
3465 | 308 |
\ : set evs"; |
4470 | 309 |
by (blast_tac (claset() addSIs [NA_Crypt_imp_Server_msg]) 1); |
2328 | 310 |
qed "A_trusts_OR4"; |
2014
5be4c8ca7b25
Correction of protocol; addition of Reveal message; proofs of
paulson
parents:
1999
diff
changeset
|
311 |
|
5be4c8ca7b25
Correction of protocol; addition of Reveal message; proofs of
paulson
parents:
1999
diff
changeset
|
312 |
|
2048 | 313 |
(** Crucial secrecy property: Spy does not see the keys sent in msg OR3 |
314 |
Does not in itself guarantee security: an attack could violate |
|
315 |
the premises, e.g. by having A=Spy **) |
|
2014
5be4c8ca7b25
Correction of protocol; addition of Reveal message; proofs of
paulson
parents:
1999
diff
changeset
|
316 |
|
1941 | 317 |
goal thy |
3683 | 318 |
"!!evs. [| A ~: bad; B ~: bad; evs : otway |] \ |
3519
ab0a9fbed4c0
Changing "lost" from a parameter of protocol definitions to a constant.
paulson
parents:
3516
diff
changeset
|
319 |
\ ==> Says Server B \ |
ab0a9fbed4c0
Changing "lost" from a parameter of protocol definitions to a constant.
paulson
parents:
3516
diff
changeset
|
320 |
\ {|NA, Crypt (shrK A) {|NA, Key K|}, \ |
ab0a9fbed4c0
Changing "lost" from a parameter of protocol definitions to a constant.
paulson
parents:
3516
diff
changeset
|
321 |
\ Crypt (shrK B) {|NB, Key K|}|} : set evs --> \ |
ab0a9fbed4c0
Changing "lost" from a parameter of protocol definitions to a constant.
paulson
parents:
3516
diff
changeset
|
322 |
\ Says B Spy {|NA, NB, Key K|} ~: set evs --> \ |
3683 | 323 |
\ Key K ~: analz (spies evs)"; |
2032 | 324 |
by (etac otway.induct 1); |
3683 | 325 |
by analz_spies_tac; |
1964 | 326 |
by (ALLGOALS |
4091 | 327 |
(asm_simp_tac (simpset() addcongs [conj_cong] |
4509
828148415197
Making proofs faster, especially using keysFor_parts_insert
paulson
parents:
4477
diff
changeset
|
328 |
addsimps [analz_insert_eq, analz_insert_freshK] |
828148415197
Making proofs faster, especially using keysFor_parts_insert
paulson
parents:
4477
diff
changeset
|
329 |
addsimps (pushes@expand_ifs)))); |
3451
d10f100676d8
Made proofs more concise by replacing calls to spy_analz_tac by uses of
paulson
parents:
3207
diff
changeset
|
330 |
(*Oops*) |
4091 | 331 |
by (blast_tac (claset() addSDs [unique_session_keys]) 4); |
3451
d10f100676d8
Made proofs more concise by replacing calls to spy_analz_tac by uses of
paulson
parents:
3207
diff
changeset
|
332 |
(*OR4*) |
d10f100676d8
Made proofs more concise by replacing calls to spy_analz_tac by uses of
paulson
parents:
3207
diff
changeset
|
333 |
by (Blast_tac 3); |
1941 | 334 |
(*OR3*) |
4470 | 335 |
by (Blast_tac 2); |
3451
d10f100676d8
Made proofs more concise by replacing calls to spy_analz_tac by uses of
paulson
parents:
3207
diff
changeset
|
336 |
(*Fake*) |
d10f100676d8
Made proofs more concise by replacing calls to spy_analz_tac by uses of
paulson
parents:
3207
diff
changeset
|
337 |
by (spy_analz_tac 1); |
2014
5be4c8ca7b25
Correction of protocol; addition of Reveal message; proofs of
paulson
parents:
1999
diff
changeset
|
338 |
val lemma = result() RS mp RS mp RSN(2,rev_notE); |
5be4c8ca7b25
Correction of protocol; addition of Reveal message; proofs of
paulson
parents:
1999
diff
changeset
|
339 |
|
5be4c8ca7b25
Correction of protocol; addition of Reveal message; proofs of
paulson
parents:
1999
diff
changeset
|
340 |
goal thy |
3519
ab0a9fbed4c0
Changing "lost" from a parameter of protocol definitions to a constant.
paulson
parents:
3516
diff
changeset
|
341 |
"!!evs. [| Says Server B \ |
ab0a9fbed4c0
Changing "lost" from a parameter of protocol definitions to a constant.
paulson
parents:
3516
diff
changeset
|
342 |
\ {|NA, Crypt (shrK A) {|NA, Key K|}, \ |
ab0a9fbed4c0
Changing "lost" from a parameter of protocol definitions to a constant.
paulson
parents:
3516
diff
changeset
|
343 |
\ Crypt (shrK B) {|NB, Key K|}|} : set evs; \ |
ab0a9fbed4c0
Changing "lost" from a parameter of protocol definitions to a constant.
paulson
parents:
3516
diff
changeset
|
344 |
\ Says B Spy {|NA, NB, Key K|} ~: set evs; \ |
3683 | 345 |
\ A ~: bad; B ~: bad; evs : otway |] \ |
346 |
\ ==> Key K ~: analz (spies evs)"; |
|
2014
5be4c8ca7b25
Correction of protocol; addition of Reveal message; proofs of
paulson
parents:
1999
diff
changeset
|
347 |
by (forward_tac [Says_Server_message_form] 1 THEN assume_tac 1); |
4091 | 348 |
by (blast_tac (claset() addSEs [lemma]) 1); |
2032 | 349 |
qed "Spy_not_see_encrypted_key"; |
350 |
||
1945 | 351 |
|
2048 | 352 |
(**** Authenticity properties relating to NB ****) |
353 |
||
354 |
(*Only OR2 can have caused such a part of a message to appear. We do not |
|
2194
63a68a3a8a76
Removal of an obsolete result, and authentication of
paulson
parents:
2171
diff
changeset
|
355 |
know anything about X: it does NOT have to have the right form.*) |
2048 | 356 |
goal thy |
3683 | 357 |
"!!evs. [| B ~: bad; evs : otway |] \ |
2284
80ebd1a213fd
Swapped arguments of Crypt (for clarity and because it is conventional)
paulson
parents:
2264
diff
changeset
|
358 |
\ ==> Crypt (shrK B) {|NA, NB, Agent A, Agent B|} \ |
3683 | 359 |
\ : parts (spies evs) --> \ |
2194
63a68a3a8a76
Removal of an obsolete result, and authentication of
paulson
parents:
2171
diff
changeset
|
360 |
\ (EX X. Says B Server \ |
63a68a3a8a76
Removal of an obsolete result, and authentication of
paulson
parents:
2171
diff
changeset
|
361 |
\ {|NA, Agent A, Agent B, X, \ |
2284
80ebd1a213fd
Swapped arguments of Crypt (for clarity and because it is conventional)
paulson
parents:
2264
diff
changeset
|
362 |
\ Crypt (shrK B) {|NA, NB, Agent A, Agent B|}|} \ |
3465 | 363 |
\ : set evs)"; |
3519
ab0a9fbed4c0
Changing "lost" from a parameter of protocol definitions to a constant.
paulson
parents:
3516
diff
changeset
|
364 |
by (parts_induct_tac 1); |
3102 | 365 |
by (ALLGOALS Blast_tac); |
2194
63a68a3a8a76
Removal of an obsolete result, and authentication of
paulson
parents:
2171
diff
changeset
|
366 |
bind_thm ("Crypt_imp_OR2", result() RSN (2,rev_mp) RS exE); |
2048 | 367 |
|
368 |
||
369 |
(** The Nonce NB uniquely identifies B's message. **) |
|
370 |
||
371 |
goal thy |
|
3683 | 372 |
"!!evs. [| evs : otway; B ~: bad |] \ |
2064 | 373 |
\ ==> EX NA' A'. ALL NA A. \ |
3683 | 374 |
\ Crypt (shrK B) {|NA, NB, Agent A, Agent B|} : parts(spies evs) \ |
2048 | 375 |
\ --> NA = NA' & A = A'"; |
3519
ab0a9fbed4c0
Changing "lost" from a parameter of protocol definitions to a constant.
paulson
parents:
3516
diff
changeset
|
376 |
by (parts_induct_tac 1); |
4470 | 377 |
by (Blast_tac 1); |
4091 | 378 |
by (simp_tac (simpset() addsimps [all_conj_distrib]) 1); |
2048 | 379 |
(*OR2: creation of new Nonce. Move assertion into global context*) |
2064 | 380 |
by (expand_case_tac "NB = ?y" 1); |
4470 | 381 |
by (Blast_tac 1); |
2048 | 382 |
val lemma = result(); |
383 |
||
384 |
goal thy |
|
3683 | 385 |
"!!evs.[| Crypt (shrK B) {|NA, NB, Agent A, Agent B|} : parts(spies evs); \ |
386 |
\ Crypt (shrK B) {|NC, NB, Agent C, Agent B|} : parts(spies evs); \ |
|
387 |
\ evs : otway; B ~: bad |] \ |
|
2048 | 388 |
\ ==> NC = NA & C = A"; |
2417 | 389 |
by (prove_unique_tac lemma 1); |
2048 | 390 |
qed "unique_NB"; |
391 |
||
392 |
||
393 |
(*If the encrypted message appears, and B has used Nonce NB, |
|
394 |
then it originated with the Server!*) |
|
395 |
goal thy |
|
3683 | 396 |
"!!evs. [| B ~: bad; B ~= Spy; evs : otway |] \ |
397 |
\ ==> Crypt (shrK B) {|NB, Key K|} : parts (spies evs) \ |
|
2048 | 398 |
\ --> (ALL X'. Says B Server \ |
399 |
\ {|NA, Agent A, Agent B, X', \ |
|
2284
80ebd1a213fd
Swapped arguments of Crypt (for clarity and because it is conventional)
paulson
parents:
2264
diff
changeset
|
400 |
\ Crypt (shrK B) {|NA, NB, Agent A, Agent B|}|} \ |
3466
30791e5a69c4
Corrected indentations and margins after the renaming of "set_of_list"
paulson
parents:
3465
diff
changeset
|
401 |
\ : set evs \ |
2048 | 402 |
\ --> Says Server B \ |
2284
80ebd1a213fd
Swapped arguments of Crypt (for clarity and because it is conventional)
paulson
parents:
2264
diff
changeset
|
403 |
\ {|NA, Crypt (shrK A) {|NA, Key K|}, \ |
80ebd1a213fd
Swapped arguments of Crypt (for clarity and because it is conventional)
paulson
parents:
2264
diff
changeset
|
404 |
\ Crypt (shrK B) {|NB, Key K|}|} \ |
3465 | 405 |
\ : set evs)"; |
3519
ab0a9fbed4c0
Changing "lost" from a parameter of protocol definitions to a constant.
paulson
parents:
3516
diff
changeset
|
406 |
by (parts_induct_tac 1); |
4470 | 407 |
by (Blast_tac 1); |
2048 | 408 |
(*OR1: it cannot be a new Nonce, contradiction.*) |
4470 | 409 |
by (Blast_tac 1); |
2048 | 410 |
(*OR4*) |
4470 | 411 |
by (blast_tac (claset() addSEs [Crypt_imp_OR2]) 2); |
2194
63a68a3a8a76
Removal of an obsolete result, and authentication of
paulson
parents:
2171
diff
changeset
|
412 |
(*OR3*) |
4470 | 413 |
(*Provable in 38s by the single command |
414 |
by (blast_tac (claset() addDs [unique_NB] addEs[nonce_OR1_OR2_E]) 1); |
|
415 |
*) |
|
4091 | 416 |
by (safe_tac (claset() delrules [disjCI, impCE])); |
4470 | 417 |
by (Blast_tac 3); |
418 |
by (blast_tac (claset() addDs [unique_NB]) 2); |
|
419 |
by (blast_tac (claset() addSEs [nonce_OR1_OR2_E] |
|
420 |
delrules [conjI] (*stop split-up*)) 1); |
|
2048 | 421 |
qed_spec_mp "NB_Crypt_imp_Server_msg"; |
422 |
||
423 |
||
424 |
(*Guarantee for B: if it gets a message with matching NB then the Server |
|
425 |
has sent the correct message.*) |
|
426 |
goal thy |
|
3683 | 427 |
"!!evs. [| B ~: bad; B ~= Spy; evs : otway; \ |
428 |
\ Says S' B {|NA, X, Crypt (shrK B) {|NB, Key K|}|} : set evs; \ |
|
2048 | 429 |
\ Says B Server {|NA, Agent A, Agent B, X', \ |
2284
80ebd1a213fd
Swapped arguments of Crypt (for clarity and because it is conventional)
paulson
parents:
2264
diff
changeset
|
430 |
\ Crypt (shrK B) {|NA, NB, Agent A, Agent B|} |} \ |
3466
30791e5a69c4
Corrected indentations and margins after the renaming of "set_of_list"
paulson
parents:
3465
diff
changeset
|
431 |
\ : set evs |] \ |
2048 | 432 |
\ ==> Says Server B \ |
433 |
\ {|NA, \ |
|
2284
80ebd1a213fd
Swapped arguments of Crypt (for clarity and because it is conventional)
paulson
parents:
2264
diff
changeset
|
434 |
\ Crypt (shrK A) {|NA, Key K|}, \ |
80ebd1a213fd
Swapped arguments of Crypt (for clarity and because it is conventional)
paulson
parents:
2264
diff
changeset
|
435 |
\ Crypt (shrK B) {|NB, Key K|}|} \ |
3465 | 436 |
\ : set evs"; |
4470 | 437 |
by (blast_tac (claset() addSIs [NB_Crypt_imp_Server_msg]) 1); |
2328 | 438 |
qed "B_trusts_OR3"; |
2048 | 439 |
|
440 |
||
2328 | 441 |
B_trusts_OR3 RS Spy_not_see_encrypted_key; |
2048 | 442 |
|
443 |
||
1945 | 444 |
goal thy |
3683 | 445 |
"!!evs. [| B ~: bad; evs : otway |] \ |
3519
ab0a9fbed4c0
Changing "lost" from a parameter of protocol definitions to a constant.
paulson
parents:
3516
diff
changeset
|
446 |
\ ==> Says Server B \ |
ab0a9fbed4c0
Changing "lost" from a parameter of protocol definitions to a constant.
paulson
parents:
3516
diff
changeset
|
447 |
\ {|NA, Crypt (shrK A) {|NA, Key K|}, \ |
ab0a9fbed4c0
Changing "lost" from a parameter of protocol definitions to a constant.
paulson
parents:
3516
diff
changeset
|
448 |
\ Crypt (shrK B) {|NB, Key K|}|} : set evs --> \ |
ab0a9fbed4c0
Changing "lost" from a parameter of protocol definitions to a constant.
paulson
parents:
3516
diff
changeset
|
449 |
\ (EX X. Says B Server {|NA, Agent A, Agent B, X, \ |
2284
80ebd1a213fd
Swapped arguments of Crypt (for clarity and because it is conventional)
paulson
parents:
2264
diff
changeset
|
450 |
\ Crypt (shrK B) {|NA, NB, Agent A, Agent B|} |} \ |
3465 | 451 |
\ : set evs)"; |
2032 | 452 |
by (etac otway.induct 1); |
3102 | 453 |
by (ALLGOALS Asm_simp_tac); |
4470 | 454 |
by (blast_tac (claset() addSEs [Crypt_imp_OR2]) 3); |
3102 | 455 |
by (ALLGOALS Blast_tac); |
2194
63a68a3a8a76
Removal of an obsolete result, and authentication of
paulson
parents:
2171
diff
changeset
|
456 |
bind_thm ("OR3_imp_OR2", result() RSN (2,rev_mp) RS exE); |
63a68a3a8a76
Removal of an obsolete result, and authentication of
paulson
parents:
2171
diff
changeset
|
457 |
|
63a68a3a8a76
Removal of an obsolete result, and authentication of
paulson
parents:
2171
diff
changeset
|
458 |
|
63a68a3a8a76
Removal of an obsolete result, and authentication of
paulson
parents:
2171
diff
changeset
|
459 |
(*After getting and checking OR4, agent A can trust that B has been active. |
63a68a3a8a76
Removal of an obsolete result, and authentication of
paulson
parents:
2171
diff
changeset
|
460 |
We could probably prove that X has the expected form, but that is not |
63a68a3a8a76
Removal of an obsolete result, and authentication of
paulson
parents:
2171
diff
changeset
|
461 |
strictly necessary for authentication.*) |
63a68a3a8a76
Removal of an obsolete result, and authentication of
paulson
parents:
2171
diff
changeset
|
462 |
goal thy |
3466
30791e5a69c4
Corrected indentations and margins after the renaming of "set_of_list"
paulson
parents:
3465
diff
changeset
|
463 |
"!!evs. [| Says B' A {|NA, Crypt (shrK A) {|NA, Key K|}|} : set evs; \ |
30791e5a69c4
Corrected indentations and margins after the renaming of "set_of_list"
paulson
parents:
3465
diff
changeset
|
464 |
\ Says A B {|NA, Agent A, Agent B, \ |
30791e5a69c4
Corrected indentations and margins after the renaming of "set_of_list"
paulson
parents:
3465
diff
changeset
|
465 |
\ Crypt (shrK A) {|NA, Agent A, Agent B|}|} : set evs; \ |
3683 | 466 |
\ A ~: bad; A ~= Spy; B ~: bad; evs : otway |] \ |
3466
30791e5a69c4
Corrected indentations and margins after the renaming of "set_of_list"
paulson
parents:
3465
diff
changeset
|
467 |
\ ==> EX NB X. Says B Server {|NA, Agent A, Agent B, X, \ |
2284
80ebd1a213fd
Swapped arguments of Crypt (for clarity and because it is conventional)
paulson
parents:
2264
diff
changeset
|
468 |
\ Crypt (shrK B) {|NA, NB, Agent A, Agent B|} |}\ |
3465 | 469 |
\ : set evs"; |
4470 | 470 |
by (blast_tac (claset() addSDs [A_trusts_OR4] |
471 |
addSEs [OR3_imp_OR2]) 1); |
|
2194
63a68a3a8a76
Removal of an obsolete result, and authentication of
paulson
parents:
2171
diff
changeset
|
472 |
qed "A_auths_B"; |