author | nipkow |
Thu, 26 Jun 1997 13:20:50 +0200 | |
changeset 3465 | e85c24717cad |
parent 3451 | d10f100676d8 |
child 3466 | 30791e5a69c4 |
permissions | -rw-r--r-- |
2090 | 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. |
|
7 |
||
8 |
Simplified version with minimal encryption but explicit messages |
|
9 |
||
10 |
From page 11 of |
|
11 |
Abadi and Needham. Prudent Engineering Practice for Cryptographic Protocols. |
|
12 |
IEEE Trans. SE 22 (1), 1996 |
|
13 |
*) |
|
14 |
||
15 |
open OtwayRees_AN; |
|
16 |
||
17 |
proof_timing:=true; |
|
18 |
HOL_quantifiers := false; |
|
19 |
||
20 |
||
2331 | 21 |
(*A "possibility property": there are traces that reach the end*) |
2090 | 22 |
goal thy |
2331 | 23 |
"!!A B. [| A ~= B; A ~= Server; B ~= Server |] \ |
24 |
\ ==> EX K. EX NA. EX evs: otway lost. \ |
|
2284
80ebd1a213fd
Swapped arguments of Crypt (for clarity and because it is conventional)
paulson
parents:
2264
diff
changeset
|
25 |
\ Says B A (Crypt (shrK A) {|Nonce NA, Agent A, Agent B, Key K|}) \ |
3465 | 26 |
\ : set evs"; |
2090 | 27 |
by (REPEAT (resolve_tac [exI,bexI] 1)); |
28 |
by (rtac (otway.Nil RS otway.OR1 RS otway.OR2 RS otway.OR3 RS otway.OR4) 2); |
|
2516
4d68fbe6378b
Now with Andy Gordon's treatment of freshness to replace newN/K
paulson
parents:
2454
diff
changeset
|
29 |
by possibility_tac; |
2090 | 30 |
result(); |
31 |
||
32 |
||
33 |
(**** Inductive proofs about otway ****) |
|
34 |
||
2106 | 35 |
(*Monotonicity*) |
2090 | 36 |
goal thy "!!evs. lost' <= lost ==> otway lost' <= otway lost"; |
37 |
by (rtac subsetI 1); |
|
38 |
by (etac otway.induct 1); |
|
39 |
by (REPEAT_FIRST |
|
40 |
(best_tac (!claset addIs (impOfSubs (sees_mono RS analz_mono RS synth_mono) |
|
41 |
:: otway.intrs)))); |
|
42 |
qed "otway_mono"; |
|
43 |
||
44 |
(*Nobody sends themselves messages*) |
|
3465 | 45 |
goal thy "!!evs. evs : otway lost ==> ALL A X. Says A A X ~: set evs"; |
2090 | 46 |
by (etac otway.induct 1); |
47 |
by (Auto_tac()); |
|
48 |
qed_spec_mp "not_Says_to_self"; |
|
49 |
Addsimps [not_Says_to_self]; |
|
50 |
AddSEs [not_Says_to_self RSN (2, rev_notE)]; |
|
51 |
||
52 |
||
53 |
(** For reasoning about the encrypted portion of messages **) |
|
54 |
||
3465 | 55 |
goal thy "!!evs. Says S' B {|X, Crypt(shrK B) X'|} : set evs ==> \ |
2090 | 56 |
\ X : analz (sees lost Spy evs)"; |
3102 | 57 |
by (blast_tac (!claset addSDs [Says_imp_sees_Spy RS analz.Inj]) 1); |
2090 | 58 |
qed "OR4_analz_sees_Spy"; |
59 |
||
2284
80ebd1a213fd
Swapped arguments of Crypt (for clarity and because it is conventional)
paulson
parents:
2264
diff
changeset
|
60 |
goal thy "!!evs. Says Server B {|X, Crypt K' {|NB, a, Agent B, K|}|} \ |
3465 | 61 |
\ : set evs ==> K : parts (sees lost Spy evs)"; |
3102 | 62 |
by (blast_tac (!claset addSEs sees_Spy_partsEs) 1); |
2131 | 63 |
qed "Oops_parts_sees_Spy"; |
2090 | 64 |
|
2131 | 65 |
(*OR4_analz_sees_Spy lets us treat those cases using the same |
2090 | 66 |
argument as for the Fake case. This is possible for most, but not all, |
2131 | 67 |
proofs, since Fake messages originate from the Spy. *) |
2090 | 68 |
|
69 |
bind_thm ("OR4_parts_sees_Spy", |
|
70 |
OR4_analz_sees_Spy RS (impOfSubs analz_subset_parts)); |
|
71 |
||
3121
cbb6c0c1c58a
Conversion to use blast_tac (with other improvements)
paulson
parents:
3102
diff
changeset
|
72 |
(*For proving the easier theorems about X ~: parts (sees lost Spy evs). |
cbb6c0c1c58a
Conversion to use blast_tac (with other improvements)
paulson
parents:
3102
diff
changeset
|
73 |
We instantiate the variable to "lost" since leaving it as a Var would |
cbb6c0c1c58a
Conversion to use blast_tac (with other improvements)
paulson
parents:
3102
diff
changeset
|
74 |
interfere with simplification.*) |
cbb6c0c1c58a
Conversion to use blast_tac (with other improvements)
paulson
parents:
3102
diff
changeset
|
75 |
val parts_induct_tac = |
cbb6c0c1c58a
Conversion to use blast_tac (with other improvements)
paulson
parents:
3102
diff
changeset
|
76 |
let val tac = forw_inst_tac [("lost","lost")] |
cbb6c0c1c58a
Conversion to use blast_tac (with other improvements)
paulson
parents:
3102
diff
changeset
|
77 |
in etac otway.induct 1 THEN |
cbb6c0c1c58a
Conversion to use blast_tac (with other improvements)
paulson
parents:
3102
diff
changeset
|
78 |
tac OR4_parts_sees_Spy 6 THEN |
cbb6c0c1c58a
Conversion to use blast_tac (with other improvements)
paulson
parents:
3102
diff
changeset
|
79 |
tac Oops_parts_sees_Spy 7 THEN |
cbb6c0c1c58a
Conversion to use blast_tac (with other improvements)
paulson
parents:
3102
diff
changeset
|
80 |
prove_simple_subgoals_tac 1 |
cbb6c0c1c58a
Conversion to use blast_tac (with other improvements)
paulson
parents:
3102
diff
changeset
|
81 |
end; |
2090 | 82 |
|
83 |
||
84 |
(** Theorems of the form X ~: parts (sees lost Spy evs) imply that NOBODY |
|
85 |
sends messages containing X! **) |
|
86 |
||
87 |
(*Spy never sees another agent's shared key! (unless it's lost at start)*) |
|
88 |
goal thy |
|
2131 | 89 |
"!!evs. evs : otway lost \ |
90 |
\ ==> (Key (shrK A) : parts (sees lost Spy evs)) = (A : lost)"; |
|
3121
cbb6c0c1c58a
Conversion to use blast_tac (with other improvements)
paulson
parents:
3102
diff
changeset
|
91 |
by parts_induct_tac; |
cbb6c0c1c58a
Conversion to use blast_tac (with other improvements)
paulson
parents:
3102
diff
changeset
|
92 |
by (Fake_parts_insert_tac 1); |
cbb6c0c1c58a
Conversion to use blast_tac (with other improvements)
paulson
parents:
3102
diff
changeset
|
93 |
by (Blast_tac 1); |
2131 | 94 |
qed "Spy_see_shrK"; |
95 |
Addsimps [Spy_see_shrK]; |
|
2090 | 96 |
|
2131 | 97 |
goal thy |
98 |
"!!evs. evs : otway lost \ |
|
99 |
\ ==> (Key (shrK A) : analz (sees lost Spy evs)) = (A : lost)"; |
|
100 |
by (auto_tac(!claset addDs [impOfSubs analz_subset_parts], !simpset)); |
|
101 |
qed "Spy_analz_shrK"; |
|
102 |
Addsimps [Spy_analz_shrK]; |
|
2090 | 103 |
|
2131 | 104 |
goal thy "!!A. [| Key (shrK A) : parts (sees lost Spy evs); \ |
105 |
\ evs : otway lost |] ==> A:lost"; |
|
3102 | 106 |
by (blast_tac (!claset addDs [Spy_see_shrK]) 1); |
2131 | 107 |
qed "Spy_see_shrK_D"; |
2090 | 108 |
|
2131 | 109 |
bind_thm ("Spy_analz_shrK_D", analz_subset_parts RS subsetD RS Spy_see_shrK_D); |
110 |
AddSDs [Spy_see_shrK_D, Spy_analz_shrK_D]; |
|
2090 | 111 |
|
112 |
||
2516
4d68fbe6378b
Now with Andy Gordon's treatment of freshness to replace newN/K
paulson
parents:
2454
diff
changeset
|
113 |
(*Nobody can have used non-existent keys!*) |
4d68fbe6378b
Now with Andy Gordon's treatment of freshness to replace newN/K
paulson
parents:
2454
diff
changeset
|
114 |
goal thy "!!evs. evs : otway lost ==> \ |
4d68fbe6378b
Now with Andy Gordon's treatment of freshness to replace newN/K
paulson
parents:
2454
diff
changeset
|
115 |
\ Key K ~: used evs --> K ~: keysFor (parts (sees lost Spy evs))"; |
3121
cbb6c0c1c58a
Conversion to use blast_tac (with other improvements)
paulson
parents:
3102
diff
changeset
|
116 |
by parts_induct_tac; |
2516
4d68fbe6378b
Now with Andy Gordon's treatment of freshness to replace newN/K
paulson
parents:
2454
diff
changeset
|
117 |
(*Fake*) |
4d68fbe6378b
Now with Andy Gordon's treatment of freshness to replace newN/K
paulson
parents:
2454
diff
changeset
|
118 |
by (best_tac |
4d68fbe6378b
Now with Andy Gordon's treatment of freshness to replace newN/K
paulson
parents:
2454
diff
changeset
|
119 |
(!claset addIs [impOfSubs analz_subset_parts] |
4d68fbe6378b
Now with Andy Gordon's treatment of freshness to replace newN/K
paulson
parents:
2454
diff
changeset
|
120 |
addDs [impOfSubs (analz_subset_parts RS keysFor_mono), |
4d68fbe6378b
Now with Andy Gordon's treatment of freshness to replace newN/K
paulson
parents:
2454
diff
changeset
|
121 |
impOfSubs (parts_insert_subset_Un RS keysFor_mono)] |
3207 | 122 |
addss (!simpset)) 1); |
2516
4d68fbe6378b
Now with Andy Gordon's treatment of freshness to replace newN/K
paulson
parents:
2454
diff
changeset
|
123 |
(*OR3*) |
3102 | 124 |
by (Blast_tac 1); |
2160 | 125 |
qed_spec_mp "new_keys_not_used"; |
2090 | 126 |
|
127 |
bind_thm ("new_keys_not_analzd", |
|
128 |
[analz_subset_parts RS keysFor_mono, |
|
129 |
new_keys_not_used] MRS contra_subsetD); |
|
130 |
||
131 |
Addsimps [new_keys_not_used, new_keys_not_analzd]; |
|
132 |
||
133 |
||
134 |
||
135 |
(*** Proofs involving analz ***) |
|
136 |
||
2131 | 137 |
(*Describes the form of K and NA when the Server sends this message.*) |
2090 | 138 |
goal thy |
2516
4d68fbe6378b
Now with Andy Gordon's treatment of freshness to replace newN/K
paulson
parents:
2454
diff
changeset
|
139 |
"!!evs. [| Says Server B \ |
4d68fbe6378b
Now with Andy Gordon's treatment of freshness to replace newN/K
paulson
parents:
2454
diff
changeset
|
140 |
\ {|Crypt (shrK A) {|NA, Agent A, Agent B, Key K|}, \ |
4d68fbe6378b
Now with Andy Gordon's treatment of freshness to replace newN/K
paulson
parents:
2454
diff
changeset
|
141 |
\ Crypt (shrK B) {|NB, Agent A, Agent B, Key K|}|} \ |
3465 | 142 |
\ : set evs; \ |
2516
4d68fbe6378b
Now with Andy Gordon's treatment of freshness to replace newN/K
paulson
parents:
2454
diff
changeset
|
143 |
\ evs : otway lost |] \ |
4d68fbe6378b
Now with Andy Gordon's treatment of freshness to replace newN/K
paulson
parents:
2454
diff
changeset
|
144 |
\ ==> K ~: range shrK & (EX i. NA = Nonce i) & (EX j. NB = Nonce j)"; |
2131 | 145 |
by (etac rev_mp 1); |
146 |
by (etac otway.induct 1); |
|
3102 | 147 |
by (ALLGOALS Asm_simp_tac); |
148 |
by (Blast_tac 1); |
|
2131 | 149 |
qed "Says_Server_message_form"; |
2090 | 150 |
|
151 |
||
152 |
(*For proofs involving analz. We again instantiate the variable to "lost".*) |
|
3121
cbb6c0c1c58a
Conversion to use blast_tac (with other improvements)
paulson
parents:
3102
diff
changeset
|
153 |
val analz_sees_tac = |
2090 | 154 |
dres_inst_tac [("lost","lost")] OR4_analz_sees_Spy 6 THEN |
2131 | 155 |
forw_inst_tac [("lost","lost")] Says_Server_message_form 7 THEN |
2516
4d68fbe6378b
Now with Andy Gordon's treatment of freshness to replace newN/K
paulson
parents:
2454
diff
changeset
|
156 |
assume_tac 7 THEN |
2451
ce85a2aafc7a
Extensive tidying and simplification, largely stemming from
paulson
parents:
2417
diff
changeset
|
157 |
REPEAT ((eresolve_tac [exE, conjE] ORELSE' hyp_subst_tac) 7); |
2090 | 158 |
|
159 |
||
160 |
(**** |
|
161 |
The following is to prove theorems of the form |
|
162 |
||
2516
4d68fbe6378b
Now with Andy Gordon's treatment of freshness to replace newN/K
paulson
parents:
2454
diff
changeset
|
163 |
Key K : analz (insert (Key KAB) (sees lost Spy evs)) ==> |
2451
ce85a2aafc7a
Extensive tidying and simplification, largely stemming from
paulson
parents:
2417
diff
changeset
|
164 |
Key K : analz (sees lost Spy evs) |
2090 | 165 |
|
166 |
A more general formula must be proved inductively. |
|
167 |
****) |
|
168 |
||
169 |
||
170 |
(** Session keys are not used to encrypt other session keys **) |
|
171 |
||
172 |
(*The equality makes the induction hypothesis easier to apply*) |
|
173 |
goal thy |
|
2331 | 174 |
"!!evs. evs : otway lost ==> \ |
2516
4d68fbe6378b
Now with Andy Gordon's treatment of freshness to replace newN/K
paulson
parents:
2454
diff
changeset
|
175 |
\ ALL K KK. KK <= Compl (range shrK) --> \ |
4d68fbe6378b
Now with Andy Gordon's treatment of freshness to replace newN/K
paulson
parents:
2454
diff
changeset
|
176 |
\ (Key K : analz (Key``KK Un (sees lost Spy evs))) = \ |
4d68fbe6378b
Now with Andy Gordon's treatment of freshness to replace newN/K
paulson
parents:
2454
diff
changeset
|
177 |
\ (K : KK | Key K : analz (sees lost Spy evs))"; |
2090 | 178 |
by (etac otway.induct 1); |
3121
cbb6c0c1c58a
Conversion to use blast_tac (with other improvements)
paulson
parents:
3102
diff
changeset
|
179 |
by analz_sees_tac; |
2516
4d68fbe6378b
Now with Andy Gordon's treatment of freshness to replace newN/K
paulson
parents:
2454
diff
changeset
|
180 |
by (REPEAT_FIRST (resolve_tac [allI, impI])); |
4d68fbe6378b
Now with Andy Gordon's treatment of freshness to replace newN/K
paulson
parents:
2454
diff
changeset
|
181 |
by (REPEAT_FIRST (rtac analz_image_freshK_lemma )); |
4d68fbe6378b
Now with Andy Gordon's treatment of freshness to replace newN/K
paulson
parents:
2454
diff
changeset
|
182 |
by (ALLGOALS (asm_simp_tac analz_image_freshK_ss)); |
3451
d10f100676d8
Made proofs more concise by replacing calls to spy_analz_tac by uses of
paulson
parents:
3207
diff
changeset
|
183 |
(*Fake*) |
d10f100676d8
Made proofs more concise by replacing calls to spy_analz_tac by uses of
paulson
parents:
3207
diff
changeset
|
184 |
by (spy_analz_tac 2); |
2516
4d68fbe6378b
Now with Andy Gordon's treatment of freshness to replace newN/K
paulson
parents:
2454
diff
changeset
|
185 |
(*Base*) |
3102 | 186 |
by (Blast_tac 1); |
2516
4d68fbe6378b
Now with Andy Gordon's treatment of freshness to replace newN/K
paulson
parents:
2454
diff
changeset
|
187 |
qed_spec_mp "analz_image_freshK"; |
2090 | 188 |
|
189 |
||
190 |
goal thy |
|
2516
4d68fbe6378b
Now with Andy Gordon's treatment of freshness to replace newN/K
paulson
parents:
2454
diff
changeset
|
191 |
"!!evs. [| evs : otway lost; KAB ~: range shrK |] ==> \ |
4d68fbe6378b
Now with Andy Gordon's treatment of freshness to replace newN/K
paulson
parents:
2454
diff
changeset
|
192 |
\ Key K : analz (insert (Key KAB) (sees lost Spy evs)) = \ |
4d68fbe6378b
Now with Andy Gordon's treatment of freshness to replace newN/K
paulson
parents:
2454
diff
changeset
|
193 |
\ (K = KAB | Key K : analz (sees lost Spy evs))"; |
4d68fbe6378b
Now with Andy Gordon's treatment of freshness to replace newN/K
paulson
parents:
2454
diff
changeset
|
194 |
by (asm_simp_tac (analz_image_freshK_ss addsimps [analz_image_freshK]) 1); |
4d68fbe6378b
Now with Andy Gordon's treatment of freshness to replace newN/K
paulson
parents:
2454
diff
changeset
|
195 |
qed "analz_insert_freshK"; |
2090 | 196 |
|
197 |
||
198 |
(*** The Key K uniquely identifies the Server's message. **) |
|
199 |
||
200 |
goal thy |
|
2331 | 201 |
"!!evs. evs : otway lost ==> \ |
2090 | 202 |
\ EX A' B' NA' NB'. ALL A B NA NB. \ |
203 |
\ Says Server B \ |
|
2331 | 204 |
\ {|Crypt (shrK A) {|NA, Agent A, Agent B, K|}, \ |
3465 | 205 |
\ Crypt (shrK B) {|NB, Agent A, Agent B, K|}|} : set evs \ |
2090 | 206 |
\ --> A=A' & B=B' & NA=NA' & NB=NB'"; |
207 |
by (etac otway.induct 1); |
|
208 |
by (ALLGOALS (asm_simp_tac (!simpset addsimps [all_conj_distrib]))); |
|
209 |
by (Step_tac 1); |
|
210 |
(*Remaining cases: OR3 and OR4*) |
|
211 |
by (ex_strip_tac 2); |
|
3102 | 212 |
by (Blast_tac 2); |
2090 | 213 |
by (expand_case_tac "K = ?y" 1); |
214 |
by (REPEAT (ares_tac [refl,exI,impI,conjI] 2)); |
|
2516
4d68fbe6378b
Now with Andy Gordon's treatment of freshness to replace newN/K
paulson
parents:
2454
diff
changeset
|
215 |
(*...we assume X is a recent message and handle this case by contradiction*) |
3102 | 216 |
by (blast_tac (!claset addSEs sees_Spy_partsEs |
217 |
delrules[conjI] (*prevent splitup into 4 subgoals*)) 1); |
|
2090 | 218 |
val lemma = result(); |
219 |
||
220 |
||
221 |
goal thy |
|
222 |
"!!evs. [| Says Server B \ |
|
2284
80ebd1a213fd
Swapped arguments of Crypt (for clarity and because it is conventional)
paulson
parents:
2264
diff
changeset
|
223 |
\ {|Crypt (shrK A) {|NA, Agent A, Agent B, K|}, \ |
80ebd1a213fd
Swapped arguments of Crypt (for clarity and because it is conventional)
paulson
parents:
2264
diff
changeset
|
224 |
\ Crypt (shrK B) {|NB, Agent A, Agent B, K|}|} \ |
3465 | 225 |
\ : set evs; \ |
2090 | 226 |
\ Says Server B' \ |
2284
80ebd1a213fd
Swapped arguments of Crypt (for clarity and because it is conventional)
paulson
parents:
2264
diff
changeset
|
227 |
\ {|Crypt (shrK A') {|NA', Agent A', Agent B', K|}, \ |
80ebd1a213fd
Swapped arguments of Crypt (for clarity and because it is conventional)
paulson
parents:
2264
diff
changeset
|
228 |
\ Crypt (shrK B') {|NB', Agent A', Agent B', K|}|} \ |
3465 | 229 |
\ : set evs; \ |
2090 | 230 |
\ evs : otway lost |] \ |
231 |
\ ==> A=A' & B=B' & NA=NA' & NB=NB'"; |
|
2417 | 232 |
by (prove_unique_tac lemma 1); |
2090 | 233 |
qed "unique_session_keys"; |
234 |
||
235 |
||
236 |
||
237 |
(**** Authenticity properties relating to NA ****) |
|
238 |
||
239 |
(*If the encrypted message appears then it originated with the Server!*) |
|
240 |
goal thy |
|
241 |
"!!evs. [| A ~: lost; evs : otway lost |] \ |
|
2284
80ebd1a213fd
Swapped arguments of Crypt (for clarity and because it is conventional)
paulson
parents:
2264
diff
changeset
|
242 |
\ ==> Crypt (shrK A) {|NA, Agent A, Agent B, Key K|} \ |
2090 | 243 |
\ : parts (sees lost Spy evs) \ |
2331 | 244 |
\ --> (EX NB. Says Server B \ |
2284
80ebd1a213fd
Swapped arguments of Crypt (for clarity and because it is conventional)
paulson
parents:
2264
diff
changeset
|
245 |
\ {|Crypt (shrK A) {|NA, Agent A, Agent B, Key K|}, \ |
80ebd1a213fd
Swapped arguments of Crypt (for clarity and because it is conventional)
paulson
parents:
2264
diff
changeset
|
246 |
\ Crypt (shrK B) {|NB, Agent A, Agent B, Key K|}|} \ |
3465 | 247 |
\ : set evs)"; |
3121
cbb6c0c1c58a
Conversion to use blast_tac (with other improvements)
paulson
parents:
3102
diff
changeset
|
248 |
by parts_induct_tac; |
cbb6c0c1c58a
Conversion to use blast_tac (with other improvements)
paulson
parents:
3102
diff
changeset
|
249 |
by (Fake_parts_insert_tac 1); |
2090 | 250 |
by (ALLGOALS (asm_simp_tac (!simpset addsimps [ex_disj_distrib]))); |
251 |
(*OR3*) |
|
3102 | 252 |
by (Blast_tac 1); |
2090 | 253 |
qed_spec_mp "NA_Crypt_imp_Server_msg"; |
254 |
||
255 |
||
2454 | 256 |
(*Corollary: if A receives B's OR4 message then it originated with the Server. |
257 |
Freshness may be inferred from nonce NA.*) |
|
2090 | 258 |
goal thy |
2284
80ebd1a213fd
Swapped arguments of Crypt (for clarity and because it is conventional)
paulson
parents:
2264
diff
changeset
|
259 |
"!!evs. [| Says B' A (Crypt (shrK A) {|NA, Agent A, Agent B, Key K|}) \ |
3465 | 260 |
\ : set evs; \ |
2090 | 261 |
\ A ~: lost; evs : otway lost |] \ |
262 |
\ ==> EX NB. Says Server B \ |
|
2284
80ebd1a213fd
Swapped arguments of Crypt (for clarity and because it is conventional)
paulson
parents:
2264
diff
changeset
|
263 |
\ {|Crypt (shrK A) {|NA, Agent A, Agent B, Key K|}, \ |
80ebd1a213fd
Swapped arguments of Crypt (for clarity and because it is conventional)
paulson
parents:
2264
diff
changeset
|
264 |
\ Crypt (shrK B) {|NB, Agent A, Agent B, Key K|}|} \ |
3465 | 265 |
\ : set evs"; |
3102 | 266 |
by (blast_tac (!claset addSIs [NA_Crypt_imp_Server_msg] |
2516
4d68fbe6378b
Now with Andy Gordon's treatment of freshness to replace newN/K
paulson
parents:
2454
diff
changeset
|
267 |
addEs sees_Spy_partsEs) 1); |
2331 | 268 |
qed "A_trusts_OR4"; |
2090 | 269 |
|
270 |
||
271 |
(** Crucial secrecy property: Spy does not see the keys sent in msg OR3 |
|
272 |
Does not in itself guarantee security: an attack could violate |
|
273 |
the premises, e.g. by having A=Spy **) |
|
274 |
||
275 |
goal thy |
|
2166 | 276 |
"!!evs. [| A ~: lost; B ~: lost; evs : otway lost |] \ |
2090 | 277 |
\ ==> Says Server B \ |
2284
80ebd1a213fd
Swapped arguments of Crypt (for clarity and because it is conventional)
paulson
parents:
2264
diff
changeset
|
278 |
\ {|Crypt (shrK A) {|NA, Agent A, Agent B, Key K|}, \ |
80ebd1a213fd
Swapped arguments of Crypt (for clarity and because it is conventional)
paulson
parents:
2264
diff
changeset
|
279 |
\ Crypt (shrK B) {|NB, Agent A, Agent B, Key K|}|} \ |
3465 | 280 |
\ : set evs --> \ |
281 |
\ Says B Spy {|NA, NB, Key K|} ~: set evs --> \ |
|
2090 | 282 |
\ Key K ~: analz (sees lost Spy evs)"; |
283 |
by (etac otway.induct 1); |
|
3121
cbb6c0c1c58a
Conversion to use blast_tac (with other improvements)
paulson
parents:
3102
diff
changeset
|
284 |
by analz_sees_tac; |
2090 | 285 |
by (ALLGOALS |
2516
4d68fbe6378b
Now with Andy Gordon's treatment of freshness to replace newN/K
paulson
parents:
2454
diff
changeset
|
286 |
(asm_simp_tac (!simpset addcongs [conj_cong] |
3451
d10f100676d8
Made proofs more concise by replacing calls to spy_analz_tac by uses of
paulson
parents:
3207
diff
changeset
|
287 |
addsimps [analz_insert_eq, not_parts_not_analz, |
d10f100676d8
Made proofs more concise by replacing calls to spy_analz_tac by uses of
paulson
parents:
3207
diff
changeset
|
288 |
analz_insert_freshK] |
2516
4d68fbe6378b
Now with Andy Gordon's treatment of freshness to replace newN/K
paulson
parents:
2454
diff
changeset
|
289 |
setloop split_tac [expand_if]))); |
3451
d10f100676d8
Made proofs more concise by replacing calls to spy_analz_tac by uses of
paulson
parents:
3207
diff
changeset
|
290 |
(*Oops*) |
d10f100676d8
Made proofs more concise by replacing calls to spy_analz_tac by uses of
paulson
parents:
3207
diff
changeset
|
291 |
by (blast_tac (!claset addSDs [unique_session_keys]) 4); |
d10f100676d8
Made proofs more concise by replacing calls to spy_analz_tac by uses of
paulson
parents:
3207
diff
changeset
|
292 |
(*OR4*) |
d10f100676d8
Made proofs more concise by replacing calls to spy_analz_tac by uses of
paulson
parents:
3207
diff
changeset
|
293 |
by (Blast_tac 3); |
2090 | 294 |
(*OR3*) |
3102 | 295 |
by (blast_tac (!claset addSEs sees_Spy_partsEs |
296 |
addIs [impOfSubs analz_subset_parts]) 2); |
|
3451
d10f100676d8
Made proofs more concise by replacing calls to spy_analz_tac by uses of
paulson
parents:
3207
diff
changeset
|
297 |
(*Fake*) |
d10f100676d8
Made proofs more concise by replacing calls to spy_analz_tac by uses of
paulson
parents:
3207
diff
changeset
|
298 |
by (spy_analz_tac 1); |
2090 | 299 |
val lemma = result() RS mp RS mp RSN(2,rev_notE); |
300 |
||
301 |
goal thy |
|
2516
4d68fbe6378b
Now with Andy Gordon's treatment of freshness to replace newN/K
paulson
parents:
2454
diff
changeset
|
302 |
"!!evs. [| Says Server B \ |
4d68fbe6378b
Now with Andy Gordon's treatment of freshness to replace newN/K
paulson
parents:
2454
diff
changeset
|
303 |
\ {|Crypt (shrK A) {|NA, Agent A, Agent B, Key K|}, \ |
4d68fbe6378b
Now with Andy Gordon's treatment of freshness to replace newN/K
paulson
parents:
2454
diff
changeset
|
304 |
\ Crypt (shrK B) {|NB, Agent A, Agent B, Key K|}|} \ |
3465 | 305 |
\ : set evs; \ |
306 |
\ Says B Spy {|NA, NB, Key K|} ~: set evs; \ |
|
2516
4d68fbe6378b
Now with Andy Gordon's treatment of freshness to replace newN/K
paulson
parents:
2454
diff
changeset
|
307 |
\ A ~: lost; B ~: lost; evs : otway lost |] \ |
4d68fbe6378b
Now with Andy Gordon's treatment of freshness to replace newN/K
paulson
parents:
2454
diff
changeset
|
308 |
\ ==> Key K ~: analz (sees lost Spy evs)"; |
2090 | 309 |
by (forward_tac [Says_Server_message_form] 1 THEN assume_tac 1); |
2891 | 310 |
by (blast_tac (!claset addSEs [lemma]) 1); |
2090 | 311 |
qed "Spy_not_see_encrypted_key"; |
312 |
||
313 |
||
314 |
goal thy |
|
2516
4d68fbe6378b
Now with Andy Gordon's treatment of freshness to replace newN/K
paulson
parents:
2454
diff
changeset
|
315 |
"!!evs. [| C ~: {A,B,Server}; \ |
4d68fbe6378b
Now with Andy Gordon's treatment of freshness to replace newN/K
paulson
parents:
2454
diff
changeset
|
316 |
\ Says Server B \ |
4d68fbe6378b
Now with Andy Gordon's treatment of freshness to replace newN/K
paulson
parents:
2454
diff
changeset
|
317 |
\ {|Crypt (shrK A) {|NA, Agent A, Agent B, Key K|}, \ |
4d68fbe6378b
Now with Andy Gordon's treatment of freshness to replace newN/K
paulson
parents:
2454
diff
changeset
|
318 |
\ Crypt (shrK B) {|NB, Agent A, Agent B, Key K|}|} \ |
3465 | 319 |
\ : set evs; \ |
320 |
\ Says B Spy {|NA, NB, Key K|} ~: set evs; \ |
|
2516
4d68fbe6378b
Now with Andy Gordon's treatment of freshness to replace newN/K
paulson
parents:
2454
diff
changeset
|
321 |
\ A ~: lost; B ~: lost; evs : otway lost |] \ |
4d68fbe6378b
Now with Andy Gordon's treatment of freshness to replace newN/K
paulson
parents:
2454
diff
changeset
|
322 |
\ ==> Key K ~: analz (sees lost C evs)"; |
2090 | 323 |
by (rtac (subset_insertI RS sees_mono RS analz_mono RS contra_subsetD) 1); |
324 |
by (rtac (sees_lost_agent_subset_sees_Spy RS analz_mono RS contra_subsetD) 1); |
|
325 |
by (FIRSTGOAL (rtac Spy_not_see_encrypted_key)); |
|
2891 | 326 |
by (REPEAT_FIRST (blast_tac (!claset addIs [otway_mono RS subsetD]))); |
2090 | 327 |
qed "Agent_not_see_encrypted_key"; |
328 |
||
329 |
||
330 |
(**** Authenticity properties relating to NB ****) |
|
331 |
||
332 |
(*If the encrypted message appears then it originated with the Server!*) |
|
333 |
goal thy |
|
2106 | 334 |
"!!evs. [| B ~: lost; evs : otway lost |] \ |
2284
80ebd1a213fd
Swapped arguments of Crypt (for clarity and because it is conventional)
paulson
parents:
2264
diff
changeset
|
335 |
\ ==> Crypt (shrK B) {|NB, Agent A, Agent B, Key K|} \ |
2106 | 336 |
\ : parts (sees lost Spy evs) \ |
2090 | 337 |
\ --> (EX NA. Says Server B \ |
2284
80ebd1a213fd
Swapped arguments of Crypt (for clarity and because it is conventional)
paulson
parents:
2264
diff
changeset
|
338 |
\ {|Crypt (shrK A) {|NA, Agent A, Agent B, Key K|}, \ |
80ebd1a213fd
Swapped arguments of Crypt (for clarity and because it is conventional)
paulson
parents:
2264
diff
changeset
|
339 |
\ Crypt (shrK B) {|NB, Agent A, Agent B, Key K|}|} \ |
3465 | 340 |
\ : set evs)"; |
3121
cbb6c0c1c58a
Conversion to use blast_tac (with other improvements)
paulson
parents:
3102
diff
changeset
|
341 |
by parts_induct_tac; |
cbb6c0c1c58a
Conversion to use blast_tac (with other improvements)
paulson
parents:
3102
diff
changeset
|
342 |
by (Fake_parts_insert_tac 1); |
2090 | 343 |
by (ALLGOALS (asm_simp_tac (!simpset addsimps [ex_disj_distrib]))); |
344 |
(*OR3*) |
|
3102 | 345 |
by (Blast_tac 1); |
2090 | 346 |
qed_spec_mp "NB_Crypt_imp_Server_msg"; |
347 |
||
348 |
||
2454 | 349 |
(*Guarantee for B: if it gets a well-formed certificate then the Server |
350 |
has sent the correct message in round 3.*) |
|
2090 | 351 |
goal thy |
2106 | 352 |
"!!evs. [| B ~: lost; evs : otway lost; \ |
2837
dee1c7f1f576
Trivial renamings (for consistency with CSFW papers)
paulson
parents:
2637
diff
changeset
|
353 |
\ Says S' B {|X, Crypt (shrK B) {|NB, Agent A, Agent B, Key K|}|} \ |
3465 | 354 |
\ : set evs |] \ |
2106 | 355 |
\ ==> EX NA. Says Server B \ |
2284
80ebd1a213fd
Swapped arguments of Crypt (for clarity and because it is conventional)
paulson
parents:
2264
diff
changeset
|
356 |
\ {|Crypt (shrK A) {|NA, Agent A, Agent B, Key K|}, \ |
80ebd1a213fd
Swapped arguments of Crypt (for clarity and because it is conventional)
paulson
parents:
2264
diff
changeset
|
357 |
\ Crypt (shrK B) {|NB, Agent A, Agent B, Key K|}|} \ |
3465 | 358 |
\ : set evs"; |
3102 | 359 |
by (blast_tac (!claset addSIs [NB_Crypt_imp_Server_msg] |
360 |
addEs sees_Spy_partsEs) 1); |
|
2331 | 361 |
qed "B_trusts_OR3"; |