author | haftmann |
Tue, 10 Jun 2008 15:30:59 +0200 | |
changeset 27108 | e447b3107696 |
parent 25134 | 3d4953e88449 |
child 35416 | d8d7d1b785af |
permissions | -rw-r--r-- |
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(****************************************************************************** |
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very similar to Guard except: |
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- Guard is replaced by GuardK, guard by guardK, Nonce by Key |
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- some scripts are slightly modified (+ keyset_in, kparts_parts) |
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- the hypothesis Key n ~:G (keyset G) is added |
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date: march 2002 |
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author: Frederic Blanqui |
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email: blanqui@lri.fr |
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webpage: http://www.lri.fr/~blanqui/ |
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University of Cambridge, Computer Laboratory |
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William Gates Building, JJ Thomson Avenue |
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Cambridge CB3 0FD, United Kingdom |
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******************************************************************************) |
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header{*protocol-independent confidentiality theorem on keys*} |
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theory GuardK |
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imports Analz Extensions |
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begin |
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(****************************************************************************** |
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messages where all the occurrences of Key n are |
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in a sub-message of the form Crypt (invKey K) X with K:Ks |
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******************************************************************************) |
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inductive_set |
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guardK :: "nat => key set => msg set" |
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for n :: nat and Ks :: "key set" |
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where |
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No_Key [intro]: "Key n ~:parts {X} ==> X:guardK n Ks" |
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| Guard_Key [intro]: "invKey K:Ks ==> Crypt K X:guardK n Ks" |
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| Crypt [intro]: "X:guardK n Ks ==> Crypt K X:guardK n Ks" |
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| Pair [intro]: "[| X:guardK n Ks; Y:guardK n Ks |] ==> {|X,Y|}:guardK n Ks" |
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subsection{*basic facts about @{term guardK}*} |
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lemma Nonce_is_guardK [iff]: "Nonce p:guardK n Ks" |
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by auto |
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lemma Agent_is_guardK [iff]: "Agent A:guardK n Ks" |
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by auto |
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lemma Number_is_guardK [iff]: "Number r:guardK n Ks" |
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by auto |
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lemma Key_notin_guardK: "X:guardK n Ks ==> X ~= Key n" |
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by (erule guardK.induct, auto) |
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lemma Key_notin_guardK_iff [iff]: "Key n ~:guardK n Ks" |
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by (auto dest: Key_notin_guardK) |
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lemma guardK_has_Crypt [rule_format]: "X:guardK n Ks ==> Key n:parts {X} |
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--> (EX K Y. Crypt K Y:kparts {X} & Key n:parts {Y})" |
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by (erule guardK.induct, auto) |
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lemma Key_notin_kparts_msg: "X:guardK n Ks ==> Key n ~:kparts {X}" |
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by (erule guardK.induct, auto dest: kparts_parts) |
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lemma Key_in_kparts_imp_no_guardK: "Key n:kparts H |
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==> EX X. X:H & X ~:guardK n Ks" |
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apply (drule in_kparts, clarify) |
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apply (rule_tac x=X in exI, clarify) |
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by (auto dest: Key_notin_kparts_msg) |
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lemma guardK_kparts [rule_format]: "X:guardK n Ks ==> |
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Y:kparts {X} --> Y:guardK n Ks" |
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by (erule guardK.induct, auto dest: kparts_parts parts_sub) |
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lemma guardK_Crypt: "[| Crypt K Y:guardK n Ks; K ~:invKey`Ks |] ==> Y:guardK n Ks" |
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by (ind_cases "Crypt K Y:guardK n Ks", auto) |
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lemma guardK_MPair [iff]: "({|X,Y|}:guardK n Ks) |
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= (X:guardK n Ks & Y:guardK n Ks)" |
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by (auto, (ind_cases "{|X,Y|}:guardK n Ks", auto)+) |
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lemma guardK_not_guardK [rule_format]: "X:guardK n Ks ==> |
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Crypt K Y:kparts {X} --> Key n:kparts {Y} --> Y ~:guardK n Ks" |
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by (erule guardK.induct, auto dest: guardK_kparts) |
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lemma guardK_extand: "[| X:guardK n Ks; Ks <= Ks'; |
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[| K:Ks'; K ~:Ks |] ==> Key K ~:parts {X} |] ==> X:guardK n Ks'" |
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by (erule guardK.induct, auto) |
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subsection{*guarded sets*} |
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constdefs GuardK :: "nat => key set => msg set => bool" |
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"GuardK n Ks H == ALL X. X:H --> X:guardK n Ks" |
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subsection{*basic facts about @{term GuardK}*} |
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lemma GuardK_empty [iff]: "GuardK n Ks {}" |
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by (simp add: GuardK_def) |
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lemma Key_notin_kparts [simplified]: "GuardK n Ks H ==> Key n ~:kparts H" |
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by (auto simp: GuardK_def dest: in_kparts Key_notin_kparts_msg) |
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lemma GuardK_must_decrypt: "[| GuardK n Ks H; Key n:analz H |] ==> |
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EX K Y. Crypt K Y:kparts H & Key (invKey K):kparts H" |
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apply (drule_tac P="%G. Key n:G" in analz_pparts_kparts_substD, simp) |
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by (drule must_decrypt, auto dest: Key_notin_kparts) |
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lemma GuardK_kparts [intro]: "GuardK n Ks H ==> GuardK n Ks (kparts H)" |
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by (auto simp: GuardK_def dest: in_kparts guardK_kparts) |
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lemma GuardK_mono: "[| GuardK n Ks H; G <= H |] ==> GuardK n Ks G" |
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by (auto simp: GuardK_def) |
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lemma GuardK_insert [iff]: "GuardK n Ks (insert X H) |
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= (GuardK n Ks H & X:guardK n Ks)" |
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by (auto simp: GuardK_def) |
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lemma GuardK_Un [iff]: "GuardK n Ks (G Un H) = (GuardK n Ks G & GuardK n Ks H)" |
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by (auto simp: GuardK_def) |
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lemma GuardK_synth [intro]: "GuardK n Ks G ==> GuardK n Ks (synth G)" |
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by (auto simp: GuardK_def, erule synth.induct, auto) |
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lemma GuardK_analz [intro]: "[| GuardK n Ks G; ALL K. K:Ks --> Key K ~:analz G |] |
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==> GuardK n Ks (analz G)" |
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apply (auto simp: GuardK_def) |
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apply (erule analz.induct, auto) |
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by (ind_cases "Crypt K Xa:guardK n Ks" for K Xa, auto) |
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lemma in_GuardK [dest]: "[| X:G; GuardK n Ks G |] ==> X:guardK n Ks" |
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by (auto simp: GuardK_def) |
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lemma in_synth_GuardK: "[| X:synth G; GuardK n Ks G |] ==> X:guardK n Ks" |
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by (drule GuardK_synth, auto) |
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lemma in_analz_GuardK: "[| X:analz G; GuardK n Ks G; |
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ALL K. K:Ks --> Key K ~:analz G |] ==> X:guardK n Ks" |
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by (drule GuardK_analz, auto) |
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lemma GuardK_keyset [simp]: "[| keyset G; Key n ~:G |] ==> GuardK n Ks G" |
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by (simp only: GuardK_def, clarify, drule keyset_in, auto) |
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lemma GuardK_Un_keyset: "[| GuardK n Ks G; keyset H; Key n ~:H |] |
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==> GuardK n Ks (G Un H)" |
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by auto |
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lemma in_GuardK_kparts: "[| X:G; GuardK n Ks G; Y:kparts {X} |] ==> Y:guardK n Ks" |
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by blast |
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lemma in_GuardK_kparts_neq: "[| X:G; GuardK n Ks G; Key n':kparts {X} |] |
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==> n ~= n'" |
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by (blast dest: in_GuardK_kparts) |
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lemma in_GuardK_kparts_Crypt: "[| X:G; GuardK n Ks G; is_MPair X; |
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Crypt K Y:kparts {X}; Key n:kparts {Y} |] ==> invKey K:Ks" |
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apply (drule in_GuardK, simp) |
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apply (frule guardK_not_guardK, simp+) |
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apply (drule guardK_kparts, simp) |
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by (ind_cases "Crypt K Y:guardK n Ks", auto) |
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lemma GuardK_extand: "[| GuardK n Ks G; Ks <= Ks'; |
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[| K:Ks'; K ~:Ks |] ==> Key K ~:parts G |] ==> GuardK n Ks' G" |
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by (auto simp: GuardK_def dest: guardK_extand parts_sub) |
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subsection{*set obtained by decrypting a message*} |
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abbreviation (input) |
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decrypt :: "msg set => key => msg => msg set" where |
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"decrypt H K Y == insert Y (H - {Crypt K Y})" |
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lemma analz_decrypt: "[| Crypt K Y:H; Key (invKey K):H; Key n:analz H |] |
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==> Key n:analz (decrypt H K Y)" |
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apply (drule_tac P="%H. Key n:analz H" in ssubst [OF insert_Diff]) |
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apply assumption |
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apply (simp only: analz_Crypt_if, simp) |
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done |
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lemma parts_decrypt: "[| Crypt K Y:H; X:parts (decrypt H K Y) |] ==> X:parts H" |
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by (erule parts.induct, auto intro: parts.Fst parts.Snd parts.Body) |
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subsection{*number of Crypt's in a message*} |
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consts crypt_nb :: "msg => nat" |
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recdef crypt_nb "measure size" |
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"crypt_nb (Crypt K X) = Suc (crypt_nb X)" |
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"crypt_nb {|X,Y|} = crypt_nb X + crypt_nb Y" |
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"crypt_nb X = 0" (* otherwise *) |
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subsection{*basic facts about @{term crypt_nb}*} |
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lemma non_empty_crypt_msg: "Crypt K Y:parts {X} ==> crypt_nb X \<noteq> 0" |
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by (induct X, simp_all, safe, simp_all) |
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subsection{*number of Crypt's in a message list*} |
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consts cnb :: "msg list => nat" |
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recdef cnb "measure size" |
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"cnb [] = 0" |
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"cnb (X#l) = crypt_nb X + cnb l" |
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subsection{*basic facts about @{term cnb}*} |
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lemma cnb_app [simp]: "cnb (l @ l') = cnb l + cnb l'" |
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by (induct l, auto) |
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lemma mem_cnb_minus: "x mem l ==> cnb l = crypt_nb x + (cnb l - crypt_nb x)" |
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by (induct l, auto) |
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lemmas mem_cnb_minus_substI = mem_cnb_minus [THEN ssubst] |
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lemma cnb_minus [simp]: "x mem l ==> cnb (remove l x) = cnb l - crypt_nb x" |
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apply (induct l, auto) |
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by (erule_tac l1=l and x1=x in mem_cnb_minus_substI, simp) |
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lemma parts_cnb: "Z:parts (set l) ==> |
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cnb l = (cnb l - crypt_nb Z) + crypt_nb Z" |
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by (erule parts.induct, auto simp: in_set_conv_decomp) |
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lemma non_empty_crypt: "Crypt K Y:parts (set l) ==> cnb l \<noteq> 0" |
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by (induct l, auto dest: non_empty_crypt_msg parts_insert_substD) |
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subsection{*list of kparts*} |
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lemma kparts_msg_set: "EX l. kparts {X} = set l & cnb l = crypt_nb X" |
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apply (induct X, simp_all) |
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apply (rule_tac x="[Agent agent]" in exI, simp) |
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apply (rule_tac x="[Number nat]" in exI, simp) |
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apply (rule_tac x="[Nonce nat]" in exI, simp) |
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apply (rule_tac x="[Key nat]" in exI, simp) |
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apply (rule_tac x="[Hash X]" in exI, simp) |
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apply (clarify, rule_tac x="l@la" in exI, simp) |
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by (clarify, rule_tac x="[Crypt nat X]" in exI, simp) |
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lemma kparts_set: "EX l'. kparts (set l) = set l' & cnb l' = cnb l" |
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apply (induct l) |
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apply (rule_tac x="[]" in exI, simp, clarsimp) |
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apply (subgoal_tac "EX l''. kparts {a} = set l'' & cnb l'' = crypt_nb a", clarify) |
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apply (rule_tac x="l''@l'" in exI, simp) |
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apply (rule kparts_insert_substI, simp) |
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by (rule kparts_msg_set) |
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subsection{*list corresponding to "decrypt"*} |
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constdefs decrypt' :: "msg list => key => msg => msg list" |
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"decrypt' l K Y == Y # remove l (Crypt K Y)" |
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declare decrypt'_def [simp] |
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subsection{*basic facts about @{term decrypt'}*} |
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lemma decrypt_minus: "decrypt (set l) K Y <= set (decrypt' l K Y)" |
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by (induct l, auto) |
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text{*if the analysis of a finite guarded set gives n then it must also give |
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one of the keys of Ks*} |
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lemma GuardK_invKey_by_list [rule_format]: "ALL l. cnb l = p |
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--> GuardK n Ks (set l) --> Key n:analz (set l) |
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--> (EX K. K:Ks & Key K:analz (set l))" |
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apply (induct p) |
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(* case p=0 *) |
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apply (clarify, drule GuardK_must_decrypt, simp, clarify) |
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apply (drule kparts_parts, drule non_empty_crypt, simp) |
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(* case p>0 *) |
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apply (clarify, frule GuardK_must_decrypt, simp, clarify) |
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apply (drule_tac P="%G. Key n:G" in analz_pparts_kparts_substD, simp) |
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apply (frule analz_decrypt, simp_all) |
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apply (subgoal_tac "EX l'. kparts (set l) = set l' & cnb l' = cnb l", clarsimp) |
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apply (drule_tac G="insert Y (set l' - {Crypt K Y})" |
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and H="set (decrypt' l' K Y)" in analz_sub, rule decrypt_minus) |
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apply (rule_tac analz_pparts_kparts_substI, simp) |
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apply (case_tac "K:invKey`Ks") |
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(* K:invKey`Ks *) |
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apply (clarsimp, blast) |
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(* K ~:invKey`Ks *) |
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apply (subgoal_tac "GuardK n Ks (set (decrypt' l' K Y))") |
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apply (drule_tac x="decrypt' l' K Y" in spec, simp add: mem_iff) |
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apply (subgoal_tac "Crypt K Y:parts (set l)") |
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apply (drule parts_cnb, rotate_tac -1, simp) |
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apply (clarify, drule_tac X="Key Ka" and H="insert Y (set l')" in analz_sub) |
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apply (rule insert_mono, rule set_remove) |
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apply (simp add: analz_insertD, blast) |
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(* Crypt K Y:parts (set l) *) |
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apply (blast dest: kparts_parts) |
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(* GuardK n Ks (set (decrypt' l' K Y)) *) |
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apply (rule_tac H="insert Y (set l')" in GuardK_mono) |
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apply (subgoal_tac "GuardK n Ks (set l')", simp) |
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apply (rule_tac K=K in guardK_Crypt, simp add: GuardK_def, simp) |
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apply (drule_tac t="set l'" in sym, simp) |
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apply (rule GuardK_kparts, simp, simp) |
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apply (rule_tac B="set l'" in subset_trans, rule set_remove, blast) |
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by (rule kparts_set) |
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lemma GuardK_invKey_finite: "[| Key n:analz G; GuardK n Ks G; finite G |] |
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==> EX K. K:Ks & Key K:analz G" |
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apply (drule finite_list, clarify) |
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by (rule GuardK_invKey_by_list, auto) |
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lemma GuardK_invKey: "[| Key n:analz G; GuardK n Ks G |] |
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==> EX K. K:Ks & Key K:analz G" |
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by (auto dest: analz_needs_only_finite GuardK_invKey_finite) |
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text{*if the analyse of a finite guarded set and a (possibly infinite) set of |
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keys gives n then it must also gives Ks*} |
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lemma GuardK_invKey_keyset: "[| Key n:analz (G Un H); GuardK n Ks G; finite G; |
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keyset H; Key n ~:H |] ==> EX K. K:Ks & Key K:analz (G Un H)" |
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apply (frule_tac P="%G. Key n:G" and G2=G in analz_keyset_substD, simp_all) |
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apply (drule_tac G="G Un (H Int keysfor G)" in GuardK_invKey_finite) |
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apply (auto simp: GuardK_def intro: analz_sub) |
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by (drule keyset_in, auto) |
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end |