author | nipkow |
Mon, 28 Oct 1996 15:36:18 +0100 | |
changeset 2134 | 04a71407089d |
parent 2104 | f5c9a91e4b50 |
child 2135 | 80477862ab33 |
permissions | -rw-r--r-- |
1941 | 1 |
(* Title: HOL/Auth/OtwayRees |
2 |
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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6 |
Inductive relation "otway" for the Otway-Rees protocol. |
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Version that encrypts Nonce NB |
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|
1941 | 10 |
From page 244 of |
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Burrows, Abadi and Needham. A Logic of Authentication. |
|
12 |
Proc. Royal Soc. 426 (1989) |
|
13 |
*) |
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14 |
||
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open OtwayRees; |
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16 |
||
17 |
proof_timing:=true; |
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18 |
HOL_quantifiers := false; |
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||
1996
33c42cae3dd0
Uses the improved enemy_analz_tac of Shared.ML, with simpler proofs
paulson
parents:
1967
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(*Weak liveness: there are traces that reach the end*) |
1996
33c42cae3dd0
Uses the improved enemy_analz_tac of Shared.ML, with simpler proofs
paulson
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goal thy |
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Uses the improved enemy_analz_tac of Shared.ML, with simpler proofs
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"!!A B. [| A ~= B; A ~= Server; B ~= Server |] \ |
2032 | 24 |
\ ==> EX K. EX NA. EX evs: otway lost. \ |
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\ Says B A {|Nonce NA, Crypt {|Nonce NA, Key K|} (shrK A)|} \ |
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\ : set_of_list evs"; |
1996
33c42cae3dd0
Uses the improved enemy_analz_tac of Shared.ML, with simpler proofs
paulson
parents:
1967
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27 |
by (REPEAT (resolve_tac [exI,bexI] 1)); |
2032 | 28 |
by (rtac (otway.Nil RS otway.OR1 RS otway.OR2 RS otway.OR3 RS otway.OR4) 2); |
1996
33c42cae3dd0
Uses the improved enemy_analz_tac of Shared.ML, with simpler proofs
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1967
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29 |
by (ALLGOALS (simp_tac (!simpset setsolver safe_solver))); |
33c42cae3dd0
Uses the improved enemy_analz_tac of Shared.ML, with simpler proofs
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30 |
by (REPEAT_FIRST (resolve_tac [refl, conjI])); |
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by (REPEAT_FIRST (fast_tac (!claset addss (!simpset setsolver safe_solver)))); |
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result(); |
1996
33c42cae3dd0
Uses the improved enemy_analz_tac of Shared.ML, with simpler proofs
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parents:
1967
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|
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Uses the improved enemy_analz_tac of Shared.ML, with simpler proofs
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parents:
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|
1941 | 35 |
(**** Inductive proofs about otway ****) |
36 |
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(*Monotonicity*) |
2032 | 38 |
goal thy "!!evs. lost' <= lost ==> otway lost' <= otway lost"; |
39 |
by (rtac subsetI 1); |
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40 |
by (etac otway.induct 1); |
|
41 |
by (REPEAT_FIRST |
|
42 |
(best_tac (!claset addIs (impOfSubs (sees_mono RS analz_mono RS synth_mono) |
|
43 |
:: otway.intrs)))); |
|
44 |
qed "otway_mono"; |
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45 |
||
1941 | 46 |
(*Nobody sends themselves messages*) |
2032 | 47 |
goal thy "!!evs. evs : otway lost ==> ALL A X. Says A A X ~: set_of_list evs"; |
48 |
by (etac otway.induct 1); |
|
1941 | 49 |
by (Auto_tac()); |
50 |
qed_spec_mp "not_Says_to_self"; |
|
51 |
Addsimps [not_Says_to_self]; |
|
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AddSEs [not_Says_to_self RSN (2, rev_notE)]; |
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53 |
||
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||
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(** For reasoning about the encrypted portion of messages **) |
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56 |
||
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goal thy "!!evs. Says A' B {|N, Agent A, Agent B, X|} : set_of_list evs ==> \ |
2032 | 58 |
\ X : analz (sees lost Spy evs)"; |
59 |
by (fast_tac (!claset addSDs [Says_imp_sees_Spy RS analz.Inj]) 1); |
|
60 |
qed "OR2_analz_sees_Spy"; |
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1941 | 61 |
|
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goal thy "!!evs. Says S B {|N, X, X'|} : set_of_list evs ==> \ |
2032 | 63 |
\ X : analz (sees lost Spy evs)"; |
64 |
by (fast_tac (!claset addSDs [Says_imp_sees_Spy RS analz.Inj]) 1); |
|
65 |
qed "OR4_analz_sees_Spy"; |
|
1941 | 66 |
|
1996
33c42cae3dd0
Uses the improved enemy_analz_tac of Shared.ML, with simpler proofs
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parents:
1967
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goal thy "!!evs. Says B' A {|N, Crypt {|N,K|} K'|} : set_of_list evs ==> \ |
2032 | 68 |
\ K : parts (sees lost Spy evs)"; |
1941 | 69 |
by (fast_tac (!claset addSEs partsEs |
2032 | 70 |
addSDs [Says_imp_sees_Spy RS parts.Inj]) 1); |
71 |
qed "Reveal_parts_sees_Spy"; |
|
1941 | 72 |
|
73 |
(*OR2_analz... and OR4_analz... let us treat those cases using the same |
|
1964 | 74 |
argument as for the Fake case. This is possible for most, but not all, |
75 |
proofs: Fake does not invent new nonces (as in OR2), and of course Fake |
|
2032 | 76 |
messages originate from the Spy. *) |
1964 | 77 |
|
2032 | 78 |
bind_thm ("OR2_parts_sees_Spy", |
79 |
OR2_analz_sees_Spy RS (impOfSubs analz_subset_parts)); |
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bind_thm ("OR4_parts_sees_Spy", |
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OR4_analz_sees_Spy RS (impOfSubs analz_subset_parts)); |
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82 |
||
83 |
(*We instantiate the variable to "lost". Leaving it as a Var makes proofs |
|
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harder to complete, since simplification does less for us.*) |
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paulson
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val parts_Fake_tac = |
2032 | 86 |
let val tac = forw_inst_tac [("lost","lost")] |
87 |
in tac OR2_parts_sees_Spy 4 THEN |
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tac OR4_parts_sees_Spy 6 THEN |
|
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tac Reveal_parts_sees_Spy 7 |
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end; |
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1941 | 91 |
|
2064 | 92 |
(*For proving the easier theorems about X ~: parts (sees lost Spy evs) *) |
93 |
fun parts_induct_tac i = SELECT_GOAL |
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(DETERM (etac otway.induct 1 THEN parts_Fake_tac THEN |
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(*Fake message*) |
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TRY (best_tac (!claset addDs [impOfSubs analz_subset_parts, |
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impOfSubs Fake_parts_insert] |
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addss (!simpset)) 2)) THEN |
|
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(*Base case*) |
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fast_tac (!claset addss (!simpset)) 1 THEN |
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ALLGOALS Asm_simp_tac) i; |
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1941 | 102 |
|
2032 | 103 |
(** Theorems of the form X ~: parts (sees lost Spy evs) imply that NOBODY |
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sends messages containing X! **) |
1941 | 105 |
|
2064 | 106 |
(*Spy never sees another agent's shared key! (unless it's lost at start)*) |
1941 | 107 |
goal thy |
2032 | 108 |
"!!evs. [| evs : otway lost; A ~: lost |] \ |
109 |
\ ==> Key (shrK A) ~: parts (sees lost Spy evs)"; |
|
2064 | 110 |
by (parts_induct_tac 1); |
1941 | 111 |
by (Auto_tac()); |
2032 | 112 |
qed "Spy_not_see_shrK"; |
1941 | 113 |
|
2032 | 114 |
bind_thm ("Spy_not_analz_shrK", |
115 |
[analz_subset_parts, Spy_not_see_shrK] MRS contra_subsetD); |
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1941 | 116 |
|
2032 | 117 |
Addsimps [Spy_not_see_shrK, Spy_not_analz_shrK]; |
1941 | 118 |
|
1964 | 119 |
(*We go to some trouble to preserve R in the 3rd and 4th subgoals |
120 |
As usual fast_tac cannot be used because it uses the equalities too soon*) |
|
1941 | 121 |
val major::prems = |
2032 | 122 |
goal thy "[| Key (shrK A) : parts (sees lost Spy evs); \ |
123 |
\ evs : otway lost; \ |
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\ A:lost ==> R \ |
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1941 | 125 |
\ |] ==> R"; |
2032 | 126 |
by (rtac ccontr 1); |
127 |
by (rtac ([major, Spy_not_see_shrK] MRS rev_notE) 1); |
|
1941 | 128 |
by (swap_res_tac prems 2); |
1967 | 129 |
by (ALLGOALS (fast_tac (!claset addIs prems))); |
2032 | 130 |
qed "Spy_see_shrK_E"; |
1941 | 131 |
|
2032 | 132 |
bind_thm ("Spy_analz_shrK_E", |
133 |
analz_subset_parts RS subsetD RS Spy_see_shrK_E); |
|
1941 | 134 |
|
2032 | 135 |
AddSEs [Spy_see_shrK_E, Spy_analz_shrK_E]; |
1941 | 136 |
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137 |
||
138 |
(*** Future keys can't be seen or used! ***) |
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139 |
||
140 |
(*Nobody can have SEEN keys that will be generated in the future. |
|
141 |
This has to be proved anew for each protocol description, |
|
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but should go by similar reasoning every time. Hardest case is the |
|
143 |
standard Fake rule. |
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144 |
The Union over C is essential for the induction! *) |
2032 | 145 |
goal thy "!!evs. evs : otway lost ==> \ |
1941 | 146 |
\ length evs <= length evs' --> \ |
2032 | 147 |
\ Key (newK evs') ~: (UN C. parts (sees lost C evs))"; |
2064 | 148 |
by (parts_induct_tac 1); |
1941 | 149 |
by (REPEAT_FIRST (best_tac (!claset addDs [impOfSubs analz_subset_parts, |
2032 | 150 |
impOfSubs parts_insert_subset_Un, |
151 |
Suc_leD] |
|
152 |
addss (!simpset)))); |
|
1941 | 153 |
val lemma = result(); |
154 |
||
155 |
(*Variant needed for the main theorem below*) |
|
156 |
goal thy |
|
2032 | 157 |
"!!evs. [| evs : otway lost; length evs <= length evs' |] \ |
158 |
\ ==> Key (newK evs') ~: parts (sees lost C evs)"; |
|
1941 | 159 |
by (fast_tac (!claset addDs [lemma]) 1); |
160 |
qed "new_keys_not_seen"; |
|
161 |
Addsimps [new_keys_not_seen]; |
|
162 |
||
163 |
(*Another variant: old messages must contain old keys!*) |
|
164 |
goal thy |
|
165 |
"!!evs. [| Says A B X : set_of_list evs; \ |
|
166 |
\ Key (newK evt) : parts {X}; \ |
|
2032 | 167 |
\ evs : otway lost \ |
1941 | 168 |
\ |] ==> length evt < length evs"; |
2032 | 169 |
by (rtac ccontr 1); |
170 |
by (dtac leI 1); |
|
171 |
by (fast_tac (!claset addSDs [new_keys_not_seen, Says_imp_sees_Spy] |
|
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172 |
addIs [impOfSubs parts_mono]) 1); |
1941 | 173 |
qed "Says_imp_old_keys"; |
174 |
||
175 |
||
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176 |
(*** Future nonces can't be seen or used! [proofs resemble those above] ***) |
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177 |
|
2032 | 178 |
goal thy "!!evs. evs : otway lost ==> \ |
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179 |
\ length evs <= length evt --> \ |
2032 | 180 |
\ Nonce (newN evt) ~: (UN C. parts (sees lost C evs))"; |
181 |
by (etac otway.induct 1); |
|
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182 |
(*auto_tac does not work here, as it performs safe_tac first*) |
2032 | 183 |
by (ALLGOALS (asm_simp_tac (!simpset addsimps [parts_insert2] |
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184 |
addcongs [disj_cong]))); |
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|
185 |
by (REPEAT_FIRST (fast_tac (!claset |
2032 | 186 |
addSEs partsEs |
187 |
addSDs [Says_imp_sees_Spy RS parts.Inj] |
|
188 |
addDs [impOfSubs analz_subset_parts, |
|
189 |
impOfSubs parts_insert_subset_Un, |
|
190 |
Suc_leD] |
|
191 |
addss (!simpset)))); |
|
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192 |
val lemma = result(); |
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193 |
|
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194 |
(*Variant needed for the main theorem below*) |
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195 |
goal thy |
2032 | 196 |
"!!evs. [| evs : otway lost; length evs <= length evs' |] \ |
197 |
\ ==> Nonce (newN evs') ~: parts (sees lost C evs)"; |
|
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|
198 |
by (fast_tac (!claset addDs [lemma]) 1); |
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|
199 |
qed "new_nonces_not_seen"; |
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|
200 |
Addsimps [new_nonces_not_seen]; |
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|
201 |
|
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|
202 |
(*Another variant: old messages must contain old nonces!*) |
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|
203 |
goal thy |
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204 |
"!!evs. [| Says A B X : set_of_list evs; \ |
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205 |
\ Nonce (newN evt) : parts {X}; \ |
2032 | 206 |
\ evs : otway lost \ |
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|
207 |
\ |] ==> length evt < length evs"; |
2032 | 208 |
by (rtac ccontr 1); |
209 |
by (dtac leI 1); |
|
210 |
by (fast_tac (!claset addSDs [new_nonces_not_seen, Says_imp_sees_Spy] |
|
211 |
addIs [impOfSubs parts_mono]) 1); |
|
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|
212 |
qed "Says_imp_old_nonces"; |
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|
213 |
|
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214 |
|
1941 | 215 |
(*Nobody can have USED keys that will be generated in the future. |
216 |
...very like new_keys_not_seen*) |
|
2032 | 217 |
goal thy "!!evs. evs : otway lost ==> \ |
1941 | 218 |
\ length evs <= length evs' --> \ |
2032 | 219 |
\ newK evs' ~: keysFor (UN C. parts (sees lost C evs))"; |
2064 | 220 |
by (parts_induct_tac 1); |
1941 | 221 |
(*OR1 and OR3*) |
222 |
by (EVERY (map (fast_tac (!claset addDs [Suc_leD] addss (!simpset))) [4,2])); |
|
223 |
(*Fake, OR2, OR4: these messages send unknown (X) components*) |
|
2104
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2071
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|
224 |
by (REPEAT |
f5c9a91e4b50
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2071
diff
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|
225 |
(best_tac |
1996
33c42cae3dd0
Uses the improved enemy_analz_tac of Shared.ML, with simpler proofs
paulson
parents:
1967
diff
changeset
|
226 |
(!claset addDs [impOfSubs (analz_subset_parts RS keysFor_mono), |
2032 | 227 |
impOfSubs (parts_insert_subset_Un RS keysFor_mono), |
228 |
Suc_leD] |
|
229 |
addEs [new_keys_not_seen RS not_parts_not_analz RSN(2,rev_notE)] |
|
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|
230 |
addss (!simpset)) 1)); |
1941 | 231 |
val lemma = result(); |
232 |
||
233 |
goal thy |
|
2032 | 234 |
"!!evs. [| evs : otway lost; length evs <= length evs' |] \ |
235 |
\ ==> newK evs' ~: keysFor (parts (sees lost C evs))"; |
|
1941 | 236 |
by (fast_tac (!claset addSDs [lemma] addss (!simpset)) 1); |
237 |
qed "new_keys_not_used"; |
|
238 |
||
239 |
bind_thm ("new_keys_not_analzd", |
|
2032 | 240 |
[analz_subset_parts RS keysFor_mono, |
241 |
new_keys_not_used] MRS contra_subsetD); |
|
1941 | 242 |
|
243 |
Addsimps [new_keys_not_used, new_keys_not_analzd]; |
|
244 |
||
245 |
||
2064 | 246 |
|
247 |
(*** Proofs involving analz ***) |
|
248 |
||
249 |
(*Describes the form of Key K when the following message is sent. The use of |
|
250 |
"parts" strengthens the induction hyp for proving the Fake case. The |
|
251 |
assumption A ~: lost prevents its being a Faked message. (Based |
|
252 |
on NS_Shared/Says_S_message_form) *) |
|
253 |
goal thy |
|
254 |
"!!evs. evs: otway lost ==> \ |
|
255 |
\ Crypt {|N, Key K|} (shrK A) : parts (sees lost Spy evs) & \ |
|
256 |
\ A ~: lost --> \ |
|
257 |
\ (EX evt: otway lost. K = newK evt)"; |
|
258 |
by (parts_induct_tac 1); |
|
259 |
by (Auto_tac()); |
|
260 |
qed_spec_mp "Reveal_message_lemma"; |
|
261 |
||
262 |
(*EITHER describes the form of Key K when the following message is sent, |
|
263 |
OR reduces it to the Fake case.*) |
|
264 |
||
265 |
goal thy |
|
266 |
"!!evs. [| Says B' A {|N, Crypt {|N, Key K|} (shrK A)|} : set_of_list evs; \ |
|
267 |
\ evs : otway lost |] \ |
|
268 |
\ ==> (EX evt: otway lost. K = newK evt) \ |
|
269 |
\ | Key K : analz (sees lost Spy evs)"; |
|
270 |
br (Reveal_message_lemma RS disjCI) 1; |
|
271 |
ba 1; |
|
272 |
by (fast_tac (!claset addSDs [Says_imp_sees_Spy RS analz.Inj] |
|
273 |
addDs [impOfSubs analz_subset_parts] |
|
274 |
addss (!simpset)) 1); |
|
275 |
qed "Reveal_message_form"; |
|
276 |
||
277 |
||
278 |
(*For proofs involving analz. We again instantiate the variable to "lost".*) |
|
279 |
val analz_Fake_tac = |
|
280 |
dres_inst_tac [("lost","lost")] OR2_analz_sees_Spy 4 THEN |
|
281 |
dres_inst_tac [("lost","lost")] OR4_analz_sees_Spy 6 THEN |
|
282 |
forw_inst_tac [("lost","lost")] Reveal_message_form 7; |
|
1941 | 283 |
|
284 |
||
285 |
(**** |
|
286 |
The following is to prove theorems of the form |
|
287 |
||
2032 | 288 |
Key K : analz (insert (Key (newK evt)) (sees lost Spy evs)) ==> |
289 |
Key K : analz (sees lost Spy evs) |
|
1941 | 290 |
|
291 |
A more general formula must be proved inductively. |
|
292 |
||
293 |
****) |
|
294 |
||
295 |
||
296 |
(** Session keys are not used to encrypt other session keys **) |
|
297 |
||
2014
5be4c8ca7b25
Correction of protocol; addition of Reveal message; proofs of
paulson
parents:
1999
diff
changeset
|
298 |
(*The equality makes the induction hypothesis easier to apply*) |
1941 | 299 |
goal thy |
2032 | 300 |
"!!evs. evs : otway lost ==> \ |
301 |
\ ALL K E. (Key K : analz (Key``(newK``E) Un (sees lost Spy evs))) = \ |
|
302 |
\ (K : newK``E | Key K : analz (sees lost Spy evs))"; |
|
303 |
by (etac otway.induct 1); |
|
2064 | 304 |
by analz_Fake_tac; |
2045
ae1030e66745
Removed some dead wood. Transferred lemmas used to prove analz_image_newK
paulson
parents:
2032
diff
changeset
|
305 |
by (REPEAT_FIRST (ares_tac [allI, analz_image_newK_lemma])); |
2014
5be4c8ca7b25
Correction of protocol; addition of Reveal message; proofs of
paulson
parents:
1999
diff
changeset
|
306 |
by (REPEAT ((eresolve_tac [bexE, disjE] ORELSE' hyp_subst_tac) 7)); |
5be4c8ca7b25
Correction of protocol; addition of Reveal message; proofs of
paulson
parents:
1999
diff
changeset
|
307 |
by (ALLGOALS (*Takes 28 secs*) |
1941 | 308 |
(asm_simp_tac |
309 |
(!simpset addsimps ([insert_Key_singleton, insert_Key_image, pushKey_newK] |
|
2032 | 310 |
@ pushes) |
1941 | 311 |
setloop split_tac [expand_if]))); |
2104
f5c9a91e4b50
Replaced excluded_middle_tac by case_tac; tidied proofs
paulson
parents:
2071
diff
changeset
|
312 |
(** LEVEL 5 **) |
2014
5be4c8ca7b25
Correction of protocol; addition of Reveal message; proofs of
paulson
parents:
1999
diff
changeset
|
313 |
(*Reveal case 2, OR4, OR2, Fake*) |
2032 | 314 |
by (EVERY (map spy_analz_tac [7,5,3,2])); |
2014
5be4c8ca7b25
Correction of protocol; addition of Reveal message; proofs of
paulson
parents:
1999
diff
changeset
|
315 |
(*Reveal case 1, OR3, Base*) |
2064 | 316 |
by (REPEAT (fast_tac (!claset addIs [image_eqI] addss (!simpset)) 1)); |
1941 | 317 |
qed_spec_mp "analz_image_newK"; |
318 |
||
319 |
||
320 |
goal thy |
|
2032 | 321 |
"!!evs. evs : otway lost ==> \ |
322 |
\ Key K : analz (insert (Key (newK evt)) (sees lost Spy evs)) = \ |
|
323 |
\ (K = newK evt | Key K : analz (sees lost Spy evs))"; |
|
1941 | 324 |
by (asm_simp_tac (HOL_ss addsimps [pushKey_newK, analz_image_newK, |
2032 | 325 |
insert_Key_singleton]) 1); |
1941 | 326 |
by (Fast_tac 1); |
327 |
qed "analz_insert_Key_newK"; |
|
328 |
||
329 |
||
2026
0df5a96bf77e
Last working version prior to introduction of "lost"
paulson
parents:
2014
diff
changeset
|
330 |
(*** The Key K uniquely identifies the Server's message. **) |
2014
5be4c8ca7b25
Correction of protocol; addition of Reveal message; proofs of
paulson
parents:
1999
diff
changeset
|
331 |
|
5be4c8ca7b25
Correction of protocol; addition of Reveal message; proofs of
paulson
parents:
1999
diff
changeset
|
332 |
fun ex_strip_tac i = REPEAT (ares_tac [exI, conjI] i) THEN assume_tac (i+1); |
5be4c8ca7b25
Correction of protocol; addition of Reveal message; proofs of
paulson
parents:
1999
diff
changeset
|
333 |
|
5be4c8ca7b25
Correction of protocol; addition of Reveal message; proofs of
paulson
parents:
1999
diff
changeset
|
334 |
goal thy |
2032 | 335 |
"!!evs. evs : otway lost ==> \ |
2014
5be4c8ca7b25
Correction of protocol; addition of Reveal message; proofs of
paulson
parents:
1999
diff
changeset
|
336 |
\ EX A' B' NA' NB'. ALL A B NA NB. \ |
5be4c8ca7b25
Correction of protocol; addition of Reveal message; proofs of
paulson
parents:
1999
diff
changeset
|
337 |
\ Says Server B \ |
5be4c8ca7b25
Correction of protocol; addition of Reveal message; proofs of
paulson
parents:
1999
diff
changeset
|
338 |
\ {|NA, Crypt {|NA, K|} (shrK A), \ |
5be4c8ca7b25
Correction of protocol; addition of Reveal message; proofs of
paulson
parents:
1999
diff
changeset
|
339 |
\ Crypt {|NB, K|} (shrK B)|} : set_of_list evs --> \ |
5be4c8ca7b25
Correction of protocol; addition of Reveal message; proofs of
paulson
parents:
1999
diff
changeset
|
340 |
\ A=A' & B=B' & NA=NA' & NB=NB'"; |
2032 | 341 |
by (etac otway.induct 1); |
2014
5be4c8ca7b25
Correction of protocol; addition of Reveal message; proofs of
paulson
parents:
1999
diff
changeset
|
342 |
by (ALLGOALS (asm_simp_tac (!simpset addsimps [all_conj_distrib]))); |
5be4c8ca7b25
Correction of protocol; addition of Reveal message; proofs of
paulson
parents:
1999
diff
changeset
|
343 |
by (Step_tac 1); |
5be4c8ca7b25
Correction of protocol; addition of Reveal message; proofs of
paulson
parents:
1999
diff
changeset
|
344 |
(*Remaining cases: OR3 and OR4*) |
5be4c8ca7b25
Correction of protocol; addition of Reveal message; proofs of
paulson
parents:
1999
diff
changeset
|
345 |
by (ex_strip_tac 2); |
5be4c8ca7b25
Correction of protocol; addition of Reveal message; proofs of
paulson
parents:
1999
diff
changeset
|
346 |
by (Fast_tac 2); |
2064 | 347 |
by (expand_case_tac "K = ?y" 1); |
348 |
by (REPEAT (ares_tac [refl,exI,impI,conjI] 2)); |
|
2014
5be4c8ca7b25
Correction of protocol; addition of Reveal message; proofs of
paulson
parents:
1999
diff
changeset
|
349 |
(*...we assume X is a very new message, and handle this case by contradiction*) |
5be4c8ca7b25
Correction of protocol; addition of Reveal message; proofs of
paulson
parents:
1999
diff
changeset
|
350 |
by (fast_tac (!claset addEs [Says_imp_old_keys RS less_irrefl] |
2032 | 351 |
delrules [conjI] (*prevent split-up into 4 subgoals*) |
352 |
addss (!simpset addsimps [parts_insertI])) 1); |
|
2014
5be4c8ca7b25
Correction of protocol; addition of Reveal message; proofs of
paulson
parents:
1999
diff
changeset
|
353 |
val lemma = result(); |
5be4c8ca7b25
Correction of protocol; addition of Reveal message; proofs of
paulson
parents:
1999
diff
changeset
|
354 |
|
5be4c8ca7b25
Correction of protocol; addition of Reveal message; proofs of
paulson
parents:
1999
diff
changeset
|
355 |
goal thy |
5be4c8ca7b25
Correction of protocol; addition of Reveal message; proofs of
paulson
parents:
1999
diff
changeset
|
356 |
"!!evs. [| Says Server B \ |
5be4c8ca7b25
Correction of protocol; addition of Reveal message; proofs of
paulson
parents:
1999
diff
changeset
|
357 |
\ {|NA, Crypt {|NA, K|} (shrK A), \ |
5be4c8ca7b25
Correction of protocol; addition of Reveal message; proofs of
paulson
parents:
1999
diff
changeset
|
358 |
\ Crypt {|NB, K|} (shrK B)|} \ |
5be4c8ca7b25
Correction of protocol; addition of Reveal message; proofs of
paulson
parents:
1999
diff
changeset
|
359 |
\ : set_of_list evs; \ |
5be4c8ca7b25
Correction of protocol; addition of Reveal message; proofs of
paulson
parents:
1999
diff
changeset
|
360 |
\ Says Server B' \ |
5be4c8ca7b25
Correction of protocol; addition of Reveal message; proofs of
paulson
parents:
1999
diff
changeset
|
361 |
\ {|NA', Crypt {|NA', K|} (shrK A'), \ |
5be4c8ca7b25
Correction of protocol; addition of Reveal message; proofs of
paulson
parents:
1999
diff
changeset
|
362 |
\ Crypt {|NB', K|} (shrK B')|} \ |
5be4c8ca7b25
Correction of protocol; addition of Reveal message; proofs of
paulson
parents:
1999
diff
changeset
|
363 |
\ : set_of_list evs; \ |
2032 | 364 |
\ evs : otway lost |] \ |
2014
5be4c8ca7b25
Correction of protocol; addition of Reveal message; proofs of
paulson
parents:
1999
diff
changeset
|
365 |
\ ==> A=A' & B=B' & NA=NA' & NB=NB'"; |
2032 | 366 |
by (dtac lemma 1); |
2014
5be4c8ca7b25
Correction of protocol; addition of Reveal message; proofs of
paulson
parents:
1999
diff
changeset
|
367 |
by (REPEAT (etac exE 1)); |
5be4c8ca7b25
Correction of protocol; addition of Reveal message; proofs of
paulson
parents:
1999
diff
changeset
|
368 |
(*Duplicate the assumption*) |
5be4c8ca7b25
Correction of protocol; addition of Reveal message; proofs of
paulson
parents:
1999
diff
changeset
|
369 |
by (forw_inst_tac [("psi", "ALL C.?P(C)")] asm_rl 1); |
5be4c8ca7b25
Correction of protocol; addition of Reveal message; proofs of
paulson
parents:
1999
diff
changeset
|
370 |
by (fast_tac (!claset addSDs [spec]) 1); |
5be4c8ca7b25
Correction of protocol; addition of Reveal message; proofs of
paulson
parents:
1999
diff
changeset
|
371 |
qed "unique_session_keys"; |
5be4c8ca7b25
Correction of protocol; addition of Reveal message; proofs of
paulson
parents:
1999
diff
changeset
|
372 |
|
5be4c8ca7b25
Correction of protocol; addition of Reveal message; proofs of
paulson
parents:
1999
diff
changeset
|
373 |
|
5be4c8ca7b25
Correction of protocol; addition of Reveal message; proofs of
paulson
parents:
1999
diff
changeset
|
374 |
|
2048 | 375 |
(**** Authenticity properties relating to NA ****) |
2014
5be4c8ca7b25
Correction of protocol; addition of Reveal message; proofs of
paulson
parents:
1999
diff
changeset
|
376 |
|
5be4c8ca7b25
Correction of protocol; addition of Reveal message; proofs of
paulson
parents:
1999
diff
changeset
|
377 |
(*Only OR1 can have caused such a part of a message to appear.*) |
5be4c8ca7b25
Correction of protocol; addition of Reveal message; proofs of
paulson
parents:
1999
diff
changeset
|
378 |
goal thy |
2064 | 379 |
"!!evs. [| A ~: lost; evs : otway lost |] \ |
380 |
\ ==> Crypt {|NA, Agent A, Agent B|} (shrK A) \ |
|
381 |
\ : parts (sees lost Spy evs) --> \ |
|
382 |
\ Says A B {|NA, Agent A, Agent B, \ |
|
2014
5be4c8ca7b25
Correction of protocol; addition of Reveal message; proofs of
paulson
parents:
1999
diff
changeset
|
383 |
\ Crypt {|NA, Agent A, Agent B|} (shrK A)|} \ |
5be4c8ca7b25
Correction of protocol; addition of Reveal message; proofs of
paulson
parents:
1999
diff
changeset
|
384 |
\ : set_of_list evs"; |
2064 | 385 |
by (parts_induct_tac 1); |
2014
5be4c8ca7b25
Correction of protocol; addition of Reveal message; proofs of
paulson
parents:
1999
diff
changeset
|
386 |
qed_spec_mp "Crypt_imp_OR1"; |
5be4c8ca7b25
Correction of protocol; addition of Reveal message; proofs of
paulson
parents:
1999
diff
changeset
|
387 |
|
5be4c8ca7b25
Correction of protocol; addition of Reveal message; proofs of
paulson
parents:
1999
diff
changeset
|
388 |
|
2064 | 389 |
(** The Nonce NA uniquely identifies A's message. **) |
2014
5be4c8ca7b25
Correction of protocol; addition of Reveal message; proofs of
paulson
parents:
1999
diff
changeset
|
390 |
|
5be4c8ca7b25
Correction of protocol; addition of Reveal message; proofs of
paulson
parents:
1999
diff
changeset
|
391 |
goal thy |
2032 | 392 |
"!!evs. [| evs : otway lost; A ~: lost |] \ |
2014
5be4c8ca7b25
Correction of protocol; addition of Reveal message; proofs of
paulson
parents:
1999
diff
changeset
|
393 |
\ ==> EX B'. ALL B. \ |
2048 | 394 |
\ Crypt {|NA, Agent A, Agent B|} (shrK A) : parts (sees lost Spy evs) \ |
395 |
\ --> B = B'"; |
|
2064 | 396 |
by (parts_induct_tac 1); |
397 |
by (simp_tac (!simpset addsimps [all_conj_distrib]) 1); |
|
2026
0df5a96bf77e
Last working version prior to introduction of "lost"
paulson
parents:
2014
diff
changeset
|
398 |
(*OR1: creation of new Nonce. Move assertion into global context*) |
2064 | 399 |
by (expand_case_tac "NA = ?y" 1); |
2014
5be4c8ca7b25
Correction of protocol; addition of Reveal message; proofs of
paulson
parents:
1999
diff
changeset
|
400 |
by (best_tac (!claset addSEs partsEs |
2032 | 401 |
addEs [new_nonces_not_seen RSN(2,rev_notE)]) 1); |
2014
5be4c8ca7b25
Correction of protocol; addition of Reveal message; proofs of
paulson
parents:
1999
diff
changeset
|
402 |
val lemma = result(); |
5be4c8ca7b25
Correction of protocol; addition of Reveal message; proofs of
paulson
parents:
1999
diff
changeset
|
403 |
|
5be4c8ca7b25
Correction of protocol; addition of Reveal message; proofs of
paulson
parents:
1999
diff
changeset
|
404 |
goal thy |
2048 | 405 |
"!!evs.[| Crypt {|NA, Agent A, Agent B|} (shrK A): parts(sees lost Spy evs); \ |
406 |
\ Crypt {|NA, Agent A, Agent C|} (shrK A): parts(sees lost Spy evs); \ |
|
407 |
\ evs : otway lost; A ~: lost |] \ |
|
2014
5be4c8ca7b25
Correction of protocol; addition of Reveal message; proofs of
paulson
parents:
1999
diff
changeset
|
408 |
\ ==> B = C"; |
2032 | 409 |
by (dtac lemma 1); |
410 |
by (assume_tac 1); |
|
2014
5be4c8ca7b25
Correction of protocol; addition of Reveal message; proofs of
paulson
parents:
1999
diff
changeset
|
411 |
by (etac exE 1); |
5be4c8ca7b25
Correction of protocol; addition of Reveal message; proofs of
paulson
parents:
1999
diff
changeset
|
412 |
(*Duplicate the assumption*) |
5be4c8ca7b25
Correction of protocol; addition of Reveal message; proofs of
paulson
parents:
1999
diff
changeset
|
413 |
by (forw_inst_tac [("psi", "ALL C.?P(C)")] asm_rl 1); |
5be4c8ca7b25
Correction of protocol; addition of Reveal message; proofs of
paulson
parents:
1999
diff
changeset
|
414 |
by (fast_tac (!claset addSDs [spec]) 1); |
2048 | 415 |
qed "unique_NA"; |
2014
5be4c8ca7b25
Correction of protocol; addition of Reveal message; proofs of
paulson
parents:
1999
diff
changeset
|
416 |
|
5be4c8ca7b25
Correction of protocol; addition of Reveal message; proofs of
paulson
parents:
1999
diff
changeset
|
417 |
|
5be4c8ca7b25
Correction of protocol; addition of Reveal message; proofs of
paulson
parents:
1999
diff
changeset
|
418 |
val nonce_not_seen_now = le_refl RSN (2, new_nonces_not_seen) RSN (2,rev_notE); |
5be4c8ca7b25
Correction of protocol; addition of Reveal message; proofs of
paulson
parents:
1999
diff
changeset
|
419 |
|
5be4c8ca7b25
Correction of protocol; addition of Reveal message; proofs of
paulson
parents:
1999
diff
changeset
|
420 |
(*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
|
421 |
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
|
422 |
over-simplified version of this protocol: see OtwayRees_Bad.*) |
5be4c8ca7b25
Correction of protocol; addition of Reveal message; proofs of
paulson
parents:
1999
diff
changeset
|
423 |
goal thy |
2032 | 424 |
"!!evs. [| A ~: lost; evs : otway lost |] \ |
2014
5be4c8ca7b25
Correction of protocol; addition of Reveal message; proofs of
paulson
parents:
1999
diff
changeset
|
425 |
\ ==> Crypt {|NA, Agent A, Agent B|} (shrK A) \ |
2032 | 426 |
\ : parts (sees lost Spy evs) --> \ |
2014
5be4c8ca7b25
Correction of protocol; addition of Reveal message; proofs of
paulson
parents:
1999
diff
changeset
|
427 |
\ Crypt {|NA', NA, Agent A', Agent A|} (shrK A) \ |
2032 | 428 |
\ ~: parts (sees lost Spy evs)"; |
2071
0debdc018d26
Put in a simpler and *much* faster proof of no_nonce_OR1_OR2
paulson
parents:
2064
diff
changeset
|
429 |
by (parts_induct_tac 1); |
0debdc018d26
Put in a simpler and *much* faster proof of no_nonce_OR1_OR2
paulson
parents:
2064
diff
changeset
|
430 |
by (REPEAT (fast_tac (!claset addSEs (partsEs@[nonce_not_seen_now]) |
2026
0df5a96bf77e
Last working version prior to introduction of "lost"
paulson
parents:
2014
diff
changeset
|
431 |
addSDs [impOfSubs parts_insert_subset_Un] |
2071
0debdc018d26
Put in a simpler and *much* faster proof of no_nonce_OR1_OR2
paulson
parents:
2064
diff
changeset
|
432 |
addss (!simpset)) 1)); |
2014
5be4c8ca7b25
Correction of protocol; addition of Reveal message; proofs of
paulson
parents:
1999
diff
changeset
|
433 |
qed_spec_mp"no_nonce_OR1_OR2"; |
5be4c8ca7b25
Correction of protocol; addition of Reveal message; proofs of
paulson
parents:
1999
diff
changeset
|
434 |
|
5be4c8ca7b25
Correction of protocol; addition of Reveal message; proofs of
paulson
parents:
1999
diff
changeset
|
435 |
|
2053 | 436 |
(*Crucial property: If the encrypted message appears, and A has used NA |
437 |
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
|
438 |
goal thy |
2048 | 439 |
"!!evs. [| A ~: lost; A ~= Spy; evs : otway lost |] \ |
440 |
\ ==> Crypt {|NA, Key K|} (shrK A) : parts (sees lost Spy evs) \ |
|
441 |
\ --> Says A B {|NA, Agent A, Agent B, \ |
|
442 |
\ Crypt {|NA, Agent A, Agent B|} (shrK A)|} \ |
|
443 |
\ : set_of_list evs --> \ |
|
444 |
\ (EX NB. Says Server B \ |
|
445 |
\ {|NA, \ |
|
446 |
\ Crypt {|NA, Key K|} (shrK A), \ |
|
447 |
\ Crypt {|NB, Key K|} (shrK B)|} \ |
|
2014
5be4c8ca7b25
Correction of protocol; addition of Reveal message; proofs of
paulson
parents:
1999
diff
changeset
|
448 |
\ : set_of_list evs)"; |
2064 | 449 |
by (parts_induct_tac 1); |
2014
5be4c8ca7b25
Correction of protocol; addition of Reveal message; proofs of
paulson
parents:
1999
diff
changeset
|
450 |
(*OR1: it cannot be a new Nonce, contradiction.*) |
5be4c8ca7b25
Correction of protocol; addition of Reveal message; proofs of
paulson
parents:
1999
diff
changeset
|
451 |
by (fast_tac (!claset addSIs [parts_insertI] |
2032 | 452 |
addSEs partsEs |
453 |
addEs [Says_imp_old_nonces RS less_irrefl] |
|
454 |
addss (!simpset)) 1); |
|
2064 | 455 |
(*OR3 and OR4*) |
2014
5be4c8ca7b25
Correction of protocol; addition of Reveal message; proofs of
paulson
parents:
1999
diff
changeset
|
456 |
(*OR4*) |
5be4c8ca7b25
Correction of protocol; addition of Reveal message; proofs of
paulson
parents:
1999
diff
changeset
|
457 |
by (REPEAT (Safe_step_tac 2)); |
5be4c8ca7b25
Correction of protocol; addition of Reveal message; proofs of
paulson
parents:
1999
diff
changeset
|
458 |
by (REPEAT (best_tac (!claset addSDs [parts_cut]) 3)); |
5be4c8ca7b25
Correction of protocol; addition of Reveal message; proofs of
paulson
parents:
1999
diff
changeset
|
459 |
by (fast_tac (!claset addSIs [Crypt_imp_OR1] |
2032 | 460 |
addEs partsEs |
461 |
addDs [Says_imp_sees_Spy RS parts.Inj]) 2); |
|
2064 | 462 |
(*OR3*) (** LEVEL 5 **) |
463 |
by (asm_simp_tac (!simpset addsimps [ex_disj_distrib]) 1); |
|
2014
5be4c8ca7b25
Correction of protocol; addition of Reveal message; proofs of
paulson
parents:
1999
diff
changeset
|
464 |
by (step_tac (!claset delrules [disjCI, impCE]) 1); |
5be4c8ca7b25
Correction of protocol; addition of Reveal message; proofs of
paulson
parents:
1999
diff
changeset
|
465 |
by (fast_tac (!claset addSEs [MPair_parts] |
2032 | 466 |
addSDs [Says_imp_sees_Spy RS parts.Inj] |
2014
5be4c8ca7b25
Correction of protocol; addition of Reveal message; proofs of
paulson
parents:
1999
diff
changeset
|
467 |
addEs [no_nonce_OR1_OR2 RSN (2, rev_notE)] |
2048 | 468 |
delrules [conjI] (*stop split-up into 4 subgoals*)) 2); |
469 |
by (fast_tac (!claset addSDs [Says_imp_sees_Spy RS parts.Inj] |
|
470 |
addSEs [MPair_parts] |
|
471 |
addEs [unique_NA]) 1); |
|
472 |
qed_spec_mp "NA_Crypt_imp_Server_msg"; |
|
2014
5be4c8ca7b25
Correction of protocol; addition of Reveal message; proofs of
paulson
parents:
1999
diff
changeset
|
473 |
|
5be4c8ca7b25
Correction of protocol; addition of Reveal message; proofs of
paulson
parents:
1999
diff
changeset
|
474 |
|
2053 | 475 |
(*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
|
476 |
then the key really did come from the Server! CANNOT prove this of the |
2048 | 477 |
bad form of this protocol, even though we can prove |
2032 | 478 |
Spy_not_see_encrypted_key*) |
2014
5be4c8ca7b25
Correction of protocol; addition of Reveal message; proofs of
paulson
parents:
1999
diff
changeset
|
479 |
goal thy |
2053 | 480 |
"!!evs. [| Says B' A {|NA, Crypt {|NA, Key K|} (shrK A)|} \ |
481 |
\ : set_of_list evs; \ |
|
482 |
\ Says A B {|NA, Agent A, Agent B, \ |
|
483 |
\ Crypt {|NA, Agent A, Agent B|} (shrK A)|} \ |
|
484 |
\ : set_of_list evs; \ |
|
485 |
\ A ~: lost; A ~= Spy; evs : otway lost |] \ |
|
486 |
\ ==> EX NB. Says Server B \ |
|
2048 | 487 |
\ {|NA, \ |
488 |
\ Crypt {|NA, Key K|} (shrK A), \ |
|
489 |
\ Crypt {|NB, Key K|} (shrK B)|} \ |
|
2053 | 490 |
\ : set_of_list evs"; |
2048 | 491 |
by (fast_tac (!claset addSIs [NA_Crypt_imp_Server_msg] |
2032 | 492 |
addEs partsEs |
493 |
addDs [Says_imp_sees_Spy RS parts.Inj]) 1); |
|
2064 | 494 |
qed "A_trust_OR4"; |
2014
5be4c8ca7b25
Correction of protocol; addition of Reveal message; proofs of
paulson
parents:
1999
diff
changeset
|
495 |
|
5be4c8ca7b25
Correction of protocol; addition of Reveal message; proofs of
paulson
parents:
1999
diff
changeset
|
496 |
|
5be4c8ca7b25
Correction of protocol; addition of Reveal message; proofs of
paulson
parents:
1999
diff
changeset
|
497 |
(*Describes the form of K and NA when the Server sends this message.*) |
1941 | 498 |
goal thy |
499 |
"!!evs. [| Says Server B \ |
|
500 |
\ {|NA, Crypt {|NA, K|} (shrK A), \ |
|
501 |
\ Crypt {|NB, K|} (shrK B)|} : set_of_list evs; \ |
|
2032 | 502 |
\ evs : otway lost |] \ |
503 |
\ ==> (EX evt: otway lost. K = Key(newK evt)) & \ |
|
2048 | 504 |
\ (EX i. NA = Nonce i) & \ |
505 |
\ (EX j. NB = Nonce j)"; |
|
2032 | 506 |
by (etac rev_mp 1); |
507 |
by (etac otway.induct 1); |
|
2048 | 508 |
by (ALLGOALS (fast_tac (!claset addss (!simpset)))); |
1941 | 509 |
qed "Says_Server_message_form"; |
510 |
||
511 |
||
2048 | 512 |
(** Crucial secrecy property: Spy does not see the keys sent in msg OR3 |
513 |
Does not in itself guarantee security: an attack could violate |
|
514 |
the premises, e.g. by having A=Spy **) |
|
2014
5be4c8ca7b25
Correction of protocol; addition of Reveal message; proofs of
paulson
parents:
1999
diff
changeset
|
515 |
|
1941 | 516 |
goal thy |
2032 | 517 |
"!!evs. [| A ~: lost; B ~: lost; evs : otway lost; evt : otway lost |] \ |
2048 | 518 |
\ ==> Says Server B \ |
519 |
\ {|NA, Crypt {|NA, Key K|} (shrK A), \ |
|
520 |
\ Crypt {|NB, Key K|} (shrK B)|} : set_of_list evs --> \ |
|
521 |
\ Says A Spy {|NA, Key K|} ~: set_of_list evs --> \ |
|
522 |
\ Key K ~: analz (sees lost Spy evs)"; |
|
2032 | 523 |
by (etac otway.induct 1); |
2064 | 524 |
by analz_Fake_tac; |
2014
5be4c8ca7b25
Correction of protocol; addition of Reveal message; proofs of
paulson
parents:
1999
diff
changeset
|
525 |
by (REPEAT_FIRST (eresolve_tac [asm_rl, bexE, disjE] ORELSE' hyp_subst_tac)); |
1964 | 526 |
by (ALLGOALS |
1941 | 527 |
(asm_full_simp_tac |
528 |
(!simpset addsimps ([analz_subset_parts RS contra_subsetD, |
|
2032 | 529 |
analz_insert_Key_newK] @ pushes) |
1941 | 530 |
setloop split_tac [expand_if]))); |
531 |
(*OR3*) |
|
2014
5be4c8ca7b25
Correction of protocol; addition of Reveal message; proofs of
paulson
parents:
1999
diff
changeset
|
532 |
by (fast_tac (!claset addSIs [parts_insertI] |
2032 | 533 |
addEs [Says_imp_old_keys RS less_irrefl] |
2048 | 534 |
addss (!simpset addsimps [parts_insert2])) 3); |
2014
5be4c8ca7b25
Correction of protocol; addition of Reveal message; proofs of
paulson
parents:
1999
diff
changeset
|
535 |
(*Reveal case 2, OR4, OR2, Fake*) |
2032 | 536 |
by (REPEAT_FIRST (resolve_tac [conjI, impI] ORELSE' spy_analz_tac)); |
2104
f5c9a91e4b50
Replaced excluded_middle_tac by case_tac; tidied proofs
paulson
parents:
2071
diff
changeset
|
537 |
(*Reveal case 1*) (** LEVEL 6 **) |
f5c9a91e4b50
Replaced excluded_middle_tac by case_tac; tidied proofs
paulson
parents:
2071
diff
changeset
|
538 |
by (case_tac "Aa : lost" 1); |
2048 | 539 |
(*But this contradicts Key K ~: analz (sees lost Spy evsa) *) |
2104
f5c9a91e4b50
Replaced excluded_middle_tac by case_tac; tidied proofs
paulson
parents:
2071
diff
changeset
|
540 |
by (dtac (Says_imp_sees_Spy RS analz.Inj) 1); |
f5c9a91e4b50
Replaced excluded_middle_tac by case_tac; tidied proofs
paulson
parents:
2071
diff
changeset
|
541 |
by (fast_tac (!claset addSDs [analz.Decrypt] addss (!simpset)) 1); |
2032 | 542 |
(*So now we have Aa ~: lost *) |
2064 | 543 |
by (dtac A_trust_OR4 1); |
2014
5be4c8ca7b25
Correction of protocol; addition of Reveal message; proofs of
paulson
parents:
1999
diff
changeset
|
544 |
by (REPEAT (assume_tac 1)); |
5be4c8ca7b25
Correction of protocol; addition of Reveal message; proofs of
paulson
parents:
1999
diff
changeset
|
545 |
by (fast_tac (!claset addDs [unique_session_keys] addss (!simpset)) 1); |
5be4c8ca7b25
Correction of protocol; addition of Reveal message; proofs of
paulson
parents:
1999
diff
changeset
|
546 |
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
|
547 |
|
5be4c8ca7b25
Correction of protocol; addition of Reveal message; proofs of
paulson
parents:
1999
diff
changeset
|
548 |
goal thy |
5be4c8ca7b25
Correction of protocol; addition of Reveal message; proofs of
paulson
parents:
1999
diff
changeset
|
549 |
"!!evs. [| Says Server B \ |
2048 | 550 |
\ {|NA, Crypt {|NA, K|} (shrK A), \ |
551 |
\ Crypt {|NB, K|} (shrK B)|} : set_of_list evs; \ |
|
552 |
\ Says A Spy {|NA, K|} ~: set_of_list evs; \ |
|
2032 | 553 |
\ A ~: lost; B ~: lost; evs : otway lost |] \ |
554 |
\ ==> K ~: analz (sees lost Spy evs)"; |
|
2014
5be4c8ca7b25
Correction of protocol; addition of Reveal message; proofs of
paulson
parents:
1999
diff
changeset
|
555 |
by (forward_tac [Says_Server_message_form] 1 THEN assume_tac 1); |
5be4c8ca7b25
Correction of protocol; addition of Reveal message; proofs of
paulson
parents:
1999
diff
changeset
|
556 |
by (fast_tac (!claset addSEs [lemma]) 1); |
2032 | 557 |
qed "Spy_not_see_encrypted_key"; |
558 |
||
1945 | 559 |
|
2032 | 560 |
goal thy |
2048 | 561 |
"!!evs. [| C ~: {A,B,Server}; \ |
562 |
\ Says Server B \ |
|
563 |
\ {|NA, Crypt {|NA, K|} (shrK A), \ |
|
564 |
\ Crypt {|NB, K|} (shrK B)|} : set_of_list evs; \ |
|
565 |
\ Says A Spy {|NA, K|} ~: set_of_list evs; \ |
|
2032 | 566 |
\ A ~: lost; B ~: lost; evs : otway lost |] \ |
567 |
\ ==> K ~: analz (sees lost C evs)"; |
|
568 |
by (rtac (subset_insertI RS sees_mono RS analz_mono RS contra_subsetD) 1); |
|
569 |
by (rtac (sees_lost_agent_subset_sees_Spy RS analz_mono RS contra_subsetD) 1); |
|
570 |
by (FIRSTGOAL (rtac Spy_not_see_encrypted_key)); |
|
571 |
by (REPEAT_FIRST (fast_tac (!claset addIs [otway_mono RS subsetD]))); |
|
572 |
qed "Agent_not_see_encrypted_key"; |
|
1945 | 573 |
|
574 |
||
2048 | 575 |
(**** Authenticity properties relating to NB ****) |
576 |
||
577 |
(*Only OR2 can have caused such a part of a message to appear. We do not |
|
578 |
know anything about X'.*) |
|
579 |
goal thy |
|
580 |
"!!evs. [| B ~: lost; evs : otway lost |] \ |
|
581 |
\ ==> Crypt {|NA, NB, Agent A, Agent B|} (shrK B) \ |
|
582 |
\ : parts (sees lost Spy evs) --> \ |
|
583 |
\ (EX X'. Says B Server \ |
|
584 |
\ {|NA, Agent A, Agent B, X', \ |
|
585 |
\ Crypt {|NA, NB, Agent A, Agent B|} (shrK B)|} \ |
|
586 |
\ : set_of_list evs)"; |
|
2064 | 587 |
by (parts_induct_tac 1); |
588 |
by (auto_tac (!claset, !simpset addcongs [conj_cong])); |
|
2048 | 589 |
qed_spec_mp "Crypt_imp_OR2"; |
590 |
||
591 |
||
592 |
(** The Nonce NB uniquely identifies B's message. **) |
|
593 |
||
594 |
goal thy |
|
595 |
"!!evs. [| evs : otway lost; B ~: lost |] \ |
|
2064 | 596 |
\ ==> EX NA' A'. ALL NA A. \ |
2048 | 597 |
\ Crypt {|NA, NB, Agent A, Agent B|} (shrK B) : parts(sees lost Spy evs) \ |
598 |
\ --> NA = NA' & A = A'"; |
|
2064 | 599 |
by (parts_induct_tac 1); |
600 |
by (simp_tac (!simpset addsimps [all_conj_distrib]) 1); |
|
2048 | 601 |
(*OR2: creation of new Nonce. Move assertion into global context*) |
2064 | 602 |
by (expand_case_tac "NB = ?y" 1); |
2048 | 603 |
by (fast_tac (!claset addSEs (nonce_not_seen_now::partsEs)) 1); |
604 |
val lemma = result(); |
|
605 |
||
606 |
goal thy |
|
607 |
"!!evs.[| Crypt {|NA, NB, Agent A, Agent B|} (shrK B) \ |
|
608 |
\ : parts(sees lost Spy evs); \ |
|
609 |
\ Crypt {|NC, NB, Agent C, Agent B|} (shrK B) \ |
|
610 |
\ : parts(sees lost Spy evs); \ |
|
611 |
\ evs : otway lost; B ~: lost |] \ |
|
612 |
\ ==> NC = NA & C = A"; |
|
613 |
by (dtac lemma 1); |
|
614 |
by (assume_tac 1); |
|
615 |
by (REPEAT (etac exE 1)); |
|
616 |
(*Duplicate the assumption*) |
|
617 |
by (forw_inst_tac [("psi", "ALL C.?P(C)")] asm_rl 1); |
|
618 |
by (fast_tac (!claset addSDs [spec]) 1); |
|
619 |
qed "unique_NB"; |
|
620 |
||
621 |
||
622 |
(*If the encrypted message appears, and B has used Nonce NB, |
|
623 |
then it originated with the Server!*) |
|
624 |
goal thy |
|
625 |
"!!evs. [| B ~: lost; B ~= Spy; evs : otway lost |] \ |
|
626 |
\ ==> Crypt {|NB, Key K|} (shrK B) : parts (sees lost Spy evs) \ |
|
627 |
\ --> (ALL X'. Says B Server \ |
|
628 |
\ {|NA, Agent A, Agent B, X', \ |
|
629 |
\ Crypt {|NA, NB, Agent A, Agent B|} (shrK B)|} \ |
|
630 |
\ : set_of_list evs \ |
|
631 |
\ --> Says Server B \ |
|
632 |
\ {|NA, Crypt {|NA, Key K|} (shrK A), \ |
|
633 |
\ Crypt {|NB, Key K|} (shrK B)|} \ |
|
634 |
\ : set_of_list evs)"; |
|
2064 | 635 |
by (parts_induct_tac 1); |
2048 | 636 |
(*OR1: it cannot be a new Nonce, contradiction.*) |
637 |
by (fast_tac (!claset addSIs [parts_insertI] |
|
638 |
addSEs partsEs |
|
639 |
addEs [Says_imp_old_nonces RS less_irrefl] |
|
640 |
addss (!simpset)) 1); |
|
641 |
(*OR3 and OR4*) (** LEVEL 5 **) |
|
642 |
(*OR4*) |
|
643 |
by (REPEAT (Safe_step_tac 2)); |
|
644 |
br (Crypt_imp_OR2 RS exE) 2; |
|
645 |
by (REPEAT (fast_tac (!claset addEs partsEs) 2)); |
|
646 |
(*OR3*) (** LEVEL 8 **) |
|
647 |
by (step_tac (!claset delrules [disjCI, impCE]) 1); |
|
648 |
by (fast_tac (!claset delrules [conjI] (*stop split-up*)) 3); |
|
649 |
by (fast_tac (!claset addSDs [Says_imp_sees_Spy RS parts.Inj] |
|
650 |
addSEs [MPair_parts] |
|
651 |
addDs [unique_NB]) 2); |
|
652 |
by (fast_tac (!claset addSEs [MPair_parts] |
|
653 |
addSDs [Says_imp_sees_Spy RS parts.Inj] |
|
654 |
addSEs [no_nonce_OR1_OR2 RSN (2, rev_notE)] |
|
655 |
delrules [conjI, impCE] (*stop split-up*)) 1); |
|
656 |
qed_spec_mp "NB_Crypt_imp_Server_msg"; |
|
657 |
||
658 |
||
659 |
(*Guarantee for B: if it gets a message with matching NB then the Server |
|
660 |
has sent the correct message.*) |
|
661 |
goal thy |
|
662 |
"!!evs. [| B ~: lost; B ~= Spy; evs : otway lost; \ |
|
663 |
\ Says S B {|NA, X, Crypt {|NB, Key K|} (shrK B)|} \ |
|
664 |
\ : set_of_list evs; \ |
|
665 |
\ Says B Server {|NA, Agent A, Agent B, X', \ |
|
666 |
\ Crypt {|NA, NB, Agent A, Agent B|} \ |
|
667 |
\ (shrK B)|} \ |
|
668 |
\ : set_of_list evs |] \ |
|
669 |
\ ==> Says Server B \ |
|
670 |
\ {|NA, \ |
|
671 |
\ Crypt {|NA, Key K|} (shrK A), \ |
|
672 |
\ Crypt {|NB, Key K|} (shrK B)|} \ |
|
673 |
\ : set_of_list evs"; |
|
674 |
by (fast_tac (!claset addSIs [NB_Crypt_imp_Server_msg] |
|
675 |
addEs partsEs |
|
676 |
addDs [Says_imp_sees_Spy RS parts.Inj]) 1); |
|
2064 | 677 |
qed "B_trust_OR3"; |
2048 | 678 |
|
679 |
||
2064 | 680 |
B_trust_OR3 RS Spy_not_see_encrypted_key; |
2048 | 681 |
|
682 |
||
2026
0df5a96bf77e
Last working version prior to introduction of "lost"
paulson
parents:
2014
diff
changeset
|
683 |
(** A session key uniquely identifies a pair of senders in the message |
2048 | 684 |
encrypted by a good agent C. NEEDED? INTERESTING?**) |
1945 | 685 |
goal thy |
2032 | 686 |
"!!evs. evs : otway lost ==> \ |
2026
0df5a96bf77e
Last working version prior to introduction of "lost"
paulson
parents:
2014
diff
changeset
|
687 |
\ EX A B. ALL C N. \ |
2032 | 688 |
\ C ~: lost --> \ |
689 |
\ Crypt {|N, Key K|} (shrK C) : parts (sees lost Spy evs) --> \ |
|
2026
0df5a96bf77e
Last working version prior to introduction of "lost"
paulson
parents:
2014
diff
changeset
|
690 |
\ C=A | C=B"; |
2032 | 691 |
by (Simp_tac 1); (*Miniscoping*) |
692 |
by (etac otway.induct 1); |
|
2064 | 693 |
by analz_Fake_tac; |
2032 | 694 |
(*spy_analz_tac just does not work here: it is an entirely different proof!*) |
1945 | 695 |
by (ALLGOALS |
2026
0df5a96bf77e
Last working version prior to introduction of "lost"
paulson
parents:
2014
diff
changeset
|
696 |
(asm_simp_tac (!simpset addsimps [all_conj_distrib, ex_disj_distrib, |
2134 | 697 |
imp_conjR, parts_insert_sees, |
2032 | 698 |
parts_insert2]))); |
1945 | 699 |
by (REPEAT_FIRST (etac exE)); |
2026
0df5a96bf77e
Last working version prior to introduction of "lost"
paulson
parents:
2014
diff
changeset
|
700 |
(*OR3: extraction of K = newK evsa to global context...*) (** LEVEL 6 **) |
2064 | 701 |
by (expand_case_tac "K = ?y" 4); |
702 |
by (REPEAT (ares_tac [exI] 5)); |
|
1945 | 703 |
(*...we prove this case by contradiction: the key is too new!*) |
2026
0df5a96bf77e
Last working version prior to introduction of "lost"
paulson
parents:
2014
diff
changeset
|
704 |
by (fast_tac (!claset addSEs partsEs |
2032 | 705 |
addEs [Says_imp_old_keys RS less_irrefl] |
706 |
addss (!simpset)) 4); |
|
2026
0df5a96bf77e
Last working version prior to introduction of "lost"
paulson
parents:
2014
diff
changeset
|
707 |
(*Base, Fake, OR2, OR4*) |
0df5a96bf77e
Last working version prior to introduction of "lost"
paulson
parents:
2014
diff
changeset
|
708 |
by (REPEAT_FIRST ex_strip_tac); |
2032 | 709 |
by (dtac synth.Inj 4); |
710 |
by (dtac synth.Inj 3); |
|
2026
0df5a96bf77e
Last working version prior to introduction of "lost"
paulson
parents:
2014
diff
changeset
|
711 |
(*Now in effect there are three Fake cases*) |
0df5a96bf77e
Last working version prior to introduction of "lost"
paulson
parents:
2014
diff
changeset
|
712 |
by (REPEAT_FIRST (best_tac (!claset addDs [impOfSubs Fake_parts_insert] |
2032 | 713 |
delrules [disjCI, disjE] |
714 |
addss (!simpset)))); |
|
2014
5be4c8ca7b25
Correction of protocol; addition of Reveal message; proofs of
paulson
parents:
1999
diff
changeset
|
715 |
qed "key_identifies_senders"; |
2032 | 716 |
|
717 |