header{*The Message Theory, Modified for SET*}
theory MessageSET
imports Main Nat_Int_Bij
begin
subsection{*General Lemmas*}
text{*Needed occasionally with @{text spy_analz_tac}, e.g. in
@{text analz_insert_Key_newK}*}
lemma Un_absorb3 [simp] : "A ∪ (B ∪ A) = B ∪ A"
by blast
text{*Collapses redundant cases in the huge protocol proofs*}
lemmas disj_simps = disj_comms disj_left_absorb disj_assoc
text{*Effective with assumptions like @{term "K ∉ range pubK"} and
@{term "K ∉ invKey`range pubK"}*}
lemma notin_image_iff: "(y ∉ f`I) = (∀i∈I. f i ≠ y)"
by blast
text{*Effective with the assumption @{term "KK ⊆ - (range(invKey o pubK))"} *}
lemma disjoint_image_iff: "(A <= - (f`I)) = (∀i∈I. f i ∉ A)"
by blast
types
key = nat
consts
all_symmetric :: bool --{*true if all keys are symmetric*}
invKey :: "key=>key" --{*inverse of a symmetric key*}
specification (invKey)
invKey [simp]: "invKey (invKey K) = K"
invKey_symmetric: "all_symmetric --> invKey = id"
by (rule exI [of _ id], auto)
text{*The inverse of a symmetric key is itself; that of a public key
is the private key and vice versa*}
constdefs
symKeys :: "key set"
"symKeys == {K. invKey K = K}"
text{*Agents. We allow any number of certification authorities, cardholders
merchants, and payment gateways.*}
datatype
agent = CA nat | Cardholder nat | Merchant nat | PG nat | Spy
text{*Messages*}
datatype
msg = Agent agent --{*Agent names*}
| Number nat --{*Ordinary integers, timestamps, ...*}
| Nonce nat --{*Unguessable nonces*}
| Pan nat --{*Unguessable Primary Account Numbers (??)*}
| Key key --{*Crypto keys*}
| Hash msg --{*Hashing*}
| MPair msg msg --{*Compound messages*}
| Crypt key msg --{*Encryption, public- or shared-key*}
syntax
"@MTuple" :: "['a, args] => 'a * 'b" ("(2{|_,/ _|})")
syntax (xsymbols)
"@MTuple" :: "['a, args] => 'a * 'b" ("(2\<lbrace>_,/ _\<rbrace>)")
translations
"{|x, y, z|}" == "{|x, {|y, z|}|}"
"{|x, y|}" == "MPair x y"
constdefs
nat_of_agent :: "agent => nat"
"nat_of_agent == agent_case (curry nat2_to_nat 0)
(curry nat2_to_nat 1)
(curry nat2_to_nat 2)
(curry nat2_to_nat 3)
(nat2_to_nat (4,0))"
--{*maps each agent to a unique natural number, for specifications*}
text{*The function is indeed injective*}
lemma inj_nat_of_agent: "inj nat_of_agent"
by (simp add: nat_of_agent_def inj_on_def curry_def
nat2_to_nat_inj [THEN inj_eq] split: agent.split)
constdefs
keysFor :: "msg set => key set"
"keysFor H == invKey ` {K. ∃X. Crypt K X ∈ H}"
subsubsection{*Inductive definition of all "parts" of a message.*}
inductive_set
parts :: "msg set => msg set"
for H :: "msg set"
where
Inj [intro]: "X ∈ H ==> X ∈ parts H"
| Fst: "{|X,Y|} ∈ parts H ==> X ∈ parts H"
| Snd: "{|X,Y|} ∈ parts H ==> Y ∈ parts H"
| Body: "Crypt K X ∈ parts H ==> X ∈ parts H"
lemma parts_mono: "G<=H ==> parts(G) <= parts(H)"
apply auto
apply (erule parts.induct)
apply (auto dest: Fst Snd Body)
done
subsubsection{*Inverse of keys*}
lemma Key_image_eq [simp]: "(Key x ∈ Key`A) = (x∈A)"
by auto
lemma Nonce_Key_image_eq [simp]: "(Nonce x ∉ Key`A)"
by auto
lemma Cardholder_image_eq [simp]: "(Cardholder x ∈ Cardholder`A) = (x ∈ A)"
by auto
lemma CA_image_eq [simp]: "(CA x ∈ CA`A) = (x ∈ A)"
by auto
lemma Pan_image_eq [simp]: "(Pan x ∈ Pan`A) = (x ∈ A)"
by auto
lemma Pan_Key_image_eq [simp]: "(Pan x ∉ Key`A)"
by auto
lemma Nonce_Pan_image_eq [simp]: "(Nonce x ∉ Pan`A)"
by auto
lemma invKey_eq [simp]: "(invKey K = invKey K') = (K=K')"
apply safe
apply (drule_tac f = invKey in arg_cong, simp)
done
subsection{*keysFor operator*}
lemma keysFor_empty [simp]: "keysFor {} = {}"
by (unfold keysFor_def, blast)
lemma keysFor_Un [simp]: "keysFor (H ∪ H') = keysFor H ∪ keysFor H'"
by (unfold keysFor_def, blast)
lemma keysFor_UN [simp]: "keysFor (\<Union>i∈A. H i) = (\<Union>i∈A. keysFor (H i))"
by (unfold keysFor_def, blast)
lemma keysFor_mono: "G⊆H ==> keysFor(G) ⊆ keysFor(H)"
by (unfold keysFor_def, blast)
lemma keysFor_insert_Agent [simp]: "keysFor (insert (Agent A) H) = keysFor H"
by (unfold keysFor_def, auto)
lemma keysFor_insert_Nonce [simp]: "keysFor (insert (Nonce N) H) = keysFor H"
by (unfold keysFor_def, auto)
lemma keysFor_insert_Number [simp]: "keysFor (insert (Number N) H) = keysFor H"
by (unfold keysFor_def, auto)
lemma keysFor_insert_Key [simp]: "keysFor (insert (Key K) H) = keysFor H"
by (unfold keysFor_def, auto)
lemma keysFor_insert_Pan [simp]: "keysFor (insert (Pan A) H) = keysFor H"
by (unfold keysFor_def, auto)
lemma keysFor_insert_Hash [simp]: "keysFor (insert (Hash X) H) = keysFor H"
by (unfold keysFor_def, auto)
lemma keysFor_insert_MPair [simp]: "keysFor (insert {|X,Y|} H) = keysFor H"
by (unfold keysFor_def, auto)
lemma keysFor_insert_Crypt [simp]:
"keysFor (insert (Crypt K X) H) = insert (invKey K) (keysFor H)"
by (unfold keysFor_def, auto)
lemma keysFor_image_Key [simp]: "keysFor (Key`E) = {}"
by (unfold keysFor_def, auto)
lemma Crypt_imp_invKey_keysFor: "Crypt K X ∈ H ==> invKey K ∈ keysFor H"
by (unfold keysFor_def, blast)
subsection{*Inductive relation "parts"*}
lemma MPair_parts:
"[| {|X,Y|} ∈ parts H;
[| X ∈ parts H; Y ∈ parts H |] ==> P |] ==> P"
by (blast dest: parts.Fst parts.Snd)
declare MPair_parts [elim!] parts.Body [dest!]
text{*NB These two rules are UNSAFE in the formal sense, as they discard the
compound message. They work well on THIS FILE.
@{text MPair_parts} is left as SAFE because it speeds up proofs.
The Crypt rule is normally kept UNSAFE to avoid breaking up certificates.*}
lemma parts_increasing: "H ⊆ parts(H)"
by blast
lemmas parts_insertI = subset_insertI [THEN parts_mono, THEN subsetD, standard]
lemma parts_empty [simp]: "parts{} = {}"
apply safe
apply (erule parts.induct, blast+)
done
lemma parts_emptyE [elim!]: "X∈ parts{} ==> P"
by simp
lemma parts_singleton: "X∈ parts H ==> ∃Y∈H. X∈ parts {Y}"
by (erule parts.induct, fast+)
subsubsection{*Unions*}
lemma parts_Un_subset1: "parts(G) ∪ parts(H) ⊆ parts(G ∪ H)"
by (intro Un_least parts_mono Un_upper1 Un_upper2)
lemma parts_Un_subset2: "parts(G ∪ H) ⊆ parts(G) ∪ parts(H)"
apply (rule subsetI)
apply (erule parts.induct, blast+)
done
lemma parts_Un [simp]: "parts(G ∪ H) = parts(G) ∪ parts(H)"
by (intro equalityI parts_Un_subset1 parts_Un_subset2)
lemma parts_insert: "parts (insert X H) = parts {X} ∪ parts H"
apply (subst insert_is_Un [of _ H])
apply (simp only: parts_Un)
done
lemma parts_insert2:
"parts (insert X (insert Y H)) = parts {X} ∪ parts {Y} ∪ parts H"
apply (simp add: Un_assoc)
apply (simp add: parts_insert [symmetric])
done
lemma parts_UN_subset1: "(\<Union>x∈A. parts(H x)) ⊆ parts(\<Union>x∈A. H x)"
by (intro UN_least parts_mono UN_upper)
lemma parts_UN_subset2: "parts(\<Union>x∈A. H x) ⊆ (\<Union>x∈A. parts(H x))"
apply (rule subsetI)
apply (erule parts.induct, blast+)
done
lemma parts_UN [simp]: "parts(\<Union>x∈A. H x) = (\<Union>x∈A. parts(H x))"
by (intro equalityI parts_UN_subset1 parts_UN_subset2)
text{*This allows @{text blast} to simplify occurrences of
@{term "parts(G∪H)"} in the assumption.*}
declare parts_Un [THEN equalityD1, THEN subsetD, THEN UnE, elim!]
lemma parts_insert_subset: "insert X (parts H) ⊆ parts(insert X H)"
by (blast intro: parts_mono [THEN [2] rev_subsetD])
subsubsection{*Idempotence and transitivity*}
lemma parts_partsD [dest!]: "X∈ parts (parts H) ==> X∈ parts H"
by (erule parts.induct, blast+)
lemma parts_idem [simp]: "parts (parts H) = parts H"
by blast
lemma parts_trans: "[| X∈ parts G; G ⊆ parts H |] ==> X∈ parts H"
by (drule parts_mono, blast)
lemma parts_cut:
"[| Y∈ parts (insert X G); X∈ parts H |] ==> Y∈ parts (G ∪ H)"
by (erule parts_trans, auto)
lemma parts_cut_eq [simp]: "X∈ parts H ==> parts (insert X H) = parts H"
by (force dest!: parts_cut intro: parts_insertI)
subsubsection{*Rewrite rules for pulling out atomic messages*}
lemmas parts_insert_eq_I = equalityI [OF subsetI parts_insert_subset]
lemma parts_insert_Agent [simp]:
"parts (insert (Agent agt) H) = insert (Agent agt) (parts H)"
apply (rule parts_insert_eq_I)
apply (erule parts.induct, auto)
done
lemma parts_insert_Nonce [simp]:
"parts (insert (Nonce N) H) = insert (Nonce N) (parts H)"
apply (rule parts_insert_eq_I)
apply (erule parts.induct, auto)
done
lemma parts_insert_Number [simp]:
"parts (insert (Number N) H) = insert (Number N) (parts H)"
apply (rule parts_insert_eq_I)
apply (erule parts.induct, auto)
done
lemma parts_insert_Key [simp]:
"parts (insert (Key K) H) = insert (Key K) (parts H)"
apply (rule parts_insert_eq_I)
apply (erule parts.induct, auto)
done
lemma parts_insert_Pan [simp]:
"parts (insert (Pan A) H) = insert (Pan A) (parts H)"
apply (rule parts_insert_eq_I)
apply (erule parts.induct, auto)
done
lemma parts_insert_Hash [simp]:
"parts (insert (Hash X) H) = insert (Hash X) (parts H)"
apply (rule parts_insert_eq_I)
apply (erule parts.induct, auto)
done
lemma parts_insert_Crypt [simp]:
"parts (insert (Crypt K X) H) =
insert (Crypt K X) (parts (insert X H))"
apply (rule equalityI)
apply (rule subsetI)
apply (erule parts.induct, auto)
apply (erule parts.induct)
apply (blast intro: parts.Body)+
done
lemma parts_insert_MPair [simp]:
"parts (insert {|X,Y|} H) =
insert {|X,Y|} (parts (insert X (insert Y H)))"
apply (rule equalityI)
apply (rule subsetI)
apply (erule parts.induct, auto)
apply (erule parts.induct)
apply (blast intro: parts.Fst parts.Snd)+
done
lemma parts_image_Key [simp]: "parts (Key`N) = Key`N"
apply auto
apply (erule parts.induct, auto)
done
lemma parts_image_Pan [simp]: "parts (Pan`A) = Pan`A"
apply auto
apply (erule parts.induct, auto)
done
lemma msg_Nonce_supply: "∃N. ∀n. N≤n --> Nonce n ∉ parts {msg}"
apply (induct_tac "msg")
apply (simp_all (no_asm_simp) add: exI parts_insert2)
prefer 2 apply (blast elim!: add_leE)
apply (rule_tac x = "N + Suc nat" in exI)
apply (auto elim!: add_leE)
done
lemma msg_Number_supply: "∃N. ∀n. N<=n --> Number n ∉ parts {msg}"
apply (induct_tac "msg")
apply (simp_all (no_asm_simp) add: exI parts_insert2)
prefer 2 apply (blast elim!: add_leE)
apply (rule_tac x = "N + Suc nat" in exI, auto)
done
subsection{*Inductive relation "analz"*}
text{*Inductive definition of "analz" -- what can be broken down from a set of
messages, including keys. A form of downward closure. Pairs can
be taken apart; messages decrypted with known keys.*}
inductive_set
analz :: "msg set => msg set"
for H :: "msg set"
where
Inj [intro,simp] : "X ∈ H ==> X ∈ analz H"
| Fst: "{|X,Y|} ∈ analz H ==> X ∈ analz H"
| Snd: "{|X,Y|} ∈ analz H ==> Y ∈ analz H"
| Decrypt [dest]:
"[|Crypt K X ∈ analz H; Key(invKey K): analz H|] ==> X ∈ analz H"
lemma analz_mono: "G<=H ==> analz(G) <= analz(H)"
apply auto
apply (erule analz.induct)
apply (auto dest: Fst Snd)
done
text{*Making it safe speeds up proofs*}
lemma MPair_analz [elim!]:
"[| {|X,Y|} ∈ analz H;
[| X ∈ analz H; Y ∈ analz H |] ==> P
|] ==> P"
by (blast dest: analz.Fst analz.Snd)
lemma analz_increasing: "H ⊆ analz(H)"
by blast
lemma analz_subset_parts: "analz H ⊆ parts H"
apply (rule subsetI)
apply (erule analz.induct, blast+)
done
lemmas analz_into_parts = analz_subset_parts [THEN subsetD, standard]
lemmas not_parts_not_analz = analz_subset_parts [THEN contra_subsetD, standard]
lemma parts_analz [simp]: "parts (analz H) = parts H"
apply (rule equalityI)
apply (rule analz_subset_parts [THEN parts_mono, THEN subset_trans], simp)
apply (blast intro: analz_increasing [THEN parts_mono, THEN subsetD])
done
lemma analz_parts [simp]: "analz (parts H) = parts H"
apply auto
apply (erule analz.induct, auto)
done
lemmas analz_insertI = subset_insertI [THEN analz_mono, THEN [2] rev_subsetD, standard]
subsubsection{*General equational properties*}
lemma analz_empty [simp]: "analz{} = {}"
apply safe
apply (erule analz.induct, blast+)
done
lemma analz_Un: "analz(G) ∪ analz(H) ⊆ analz(G ∪ H)"
by (intro Un_least analz_mono Un_upper1 Un_upper2)
lemma analz_insert: "insert X (analz H) ⊆ analz(insert X H)"
by (blast intro: analz_mono [THEN [2] rev_subsetD])
subsubsection{*Rewrite rules for pulling out atomic messages*}
lemmas analz_insert_eq_I = equalityI [OF subsetI analz_insert]
lemma analz_insert_Agent [simp]:
"analz (insert (Agent agt) H) = insert (Agent agt) (analz H)"
apply (rule analz_insert_eq_I)
apply (erule analz.induct, auto)
done
lemma analz_insert_Nonce [simp]:
"analz (insert (Nonce N) H) = insert (Nonce N) (analz H)"
apply (rule analz_insert_eq_I)
apply (erule analz.induct, auto)
done
lemma analz_insert_Number [simp]:
"analz (insert (Number N) H) = insert (Number N) (analz H)"
apply (rule analz_insert_eq_I)
apply (erule analz.induct, auto)
done
lemma analz_insert_Hash [simp]:
"analz (insert (Hash X) H) = insert (Hash X) (analz H)"
apply (rule analz_insert_eq_I)
apply (erule analz.induct, auto)
done
lemma analz_insert_Key [simp]:
"K ∉ keysFor (analz H) ==>
analz (insert (Key K) H) = insert (Key K) (analz H)"
apply (unfold keysFor_def)
apply (rule analz_insert_eq_I)
apply (erule analz.induct, auto)
done
lemma analz_insert_MPair [simp]:
"analz (insert {|X,Y|} H) =
insert {|X,Y|} (analz (insert X (insert Y H)))"
apply (rule equalityI)
apply (rule subsetI)
apply (erule analz.induct, auto)
apply (erule analz.induct)
apply (blast intro: analz.Fst analz.Snd)+
done
lemma analz_insert_Crypt:
"Key (invKey K) ∉ analz H
==> analz (insert (Crypt K X) H) = insert (Crypt K X) (analz H)"
apply (rule analz_insert_eq_I)
apply (erule analz.induct, auto)
done
lemma analz_insert_Pan [simp]:
"analz (insert (Pan A) H) = insert (Pan A) (analz H)"
apply (rule analz_insert_eq_I)
apply (erule analz.induct, auto)
done
lemma lemma1: "Key (invKey K) ∈ analz H ==>
analz (insert (Crypt K X) H) ⊆
insert (Crypt K X) (analz (insert X H))"
apply (rule subsetI)
apply (erule_tac x = x in analz.induct, auto)
done
lemma lemma2: "Key (invKey K) ∈ analz H ==>
insert (Crypt K X) (analz (insert X H)) ⊆
analz (insert (Crypt K X) H)"
apply auto
apply (erule_tac x = x in analz.induct, auto)
apply (blast intro: analz_insertI analz.Decrypt)
done
lemma analz_insert_Decrypt:
"Key (invKey K) ∈ analz H ==>
analz (insert (Crypt K X) H) =
insert (Crypt K X) (analz (insert X H))"
by (intro equalityI lemma1 lemma2)
lemma analz_Crypt_if [simp]:
"analz (insert (Crypt K X) H) =
(if (Key (invKey K) ∈ analz H)
then insert (Crypt K X) (analz (insert X H))
else insert (Crypt K X) (analz H))"
by (simp add: analz_insert_Crypt analz_insert_Decrypt)
lemma analz_insert_Crypt_subset:
"analz (insert (Crypt K X) H) ⊆
insert (Crypt K X) (analz (insert X H))"
apply (rule subsetI)
apply (erule analz.induct, auto)
done
lemma analz_image_Key [simp]: "analz (Key`N) = Key`N"
apply auto
apply (erule analz.induct, auto)
done
lemma analz_image_Pan [simp]: "analz (Pan`A) = Pan`A"
apply auto
apply (erule analz.induct, auto)
done
subsubsection{*Idempotence and transitivity*}
lemma analz_analzD [dest!]: "X∈ analz (analz H) ==> X∈ analz H"
by (erule analz.induct, blast+)
lemma analz_idem [simp]: "analz (analz H) = analz H"
by blast
lemma analz_trans: "[| X∈ analz G; G ⊆ analz H |] ==> X∈ analz H"
by (drule analz_mono, blast)
lemma analz_cut: "[| Y∈ analz (insert X H); X∈ analz H |] ==> Y∈ analz H"
by (erule analz_trans, blast)
lemma analz_insert_eq: "X∈ analz H ==> analz (insert X H) = analz H"
by (blast intro: analz_cut analz_insertI)
text{*A congruence rule for "analz"*}
lemma analz_subset_cong:
"[| analz G ⊆ analz G'; analz H ⊆ analz H'
|] ==> analz (G ∪ H) ⊆ analz (G' ∪ H')"
apply clarify
apply (erule analz.induct)
apply (best intro: analz_mono [THEN subsetD])+
done
lemma analz_cong:
"[| analz G = analz G'; analz H = analz H'
|] ==> analz (G ∪ H) = analz (G' ∪ H')"
by (intro equalityI analz_subset_cong, simp_all)
lemma analz_insert_cong:
"analz H = analz H' ==> analz(insert X H) = analz(insert X H')"
by (force simp only: insert_def intro!: analz_cong)
lemma analz_trivial:
"[| ∀X Y. {|X,Y|} ∉ H; ∀X K. Crypt K X ∉ H |] ==> analz H = H"
apply safe
apply (erule analz.induct, blast+)
done
lemma analz_UN_analz_lemma:
"X∈ analz (\<Union>i∈A. analz (H i)) ==> X∈ analz (\<Union>i∈A. H i)"
apply (erule analz.induct)
apply (blast intro: analz_mono [THEN [2] rev_subsetD])+
done
lemma analz_UN_analz [simp]: "analz (\<Union>i∈A. analz (H i)) = analz (\<Union>i∈A. H i)"
by (blast intro: analz_UN_analz_lemma analz_mono [THEN [2] rev_subsetD])
subsection{*Inductive relation "synth"*}
text{*Inductive definition of "synth" -- what can be built up from a set of
messages. A form of upward closure. Pairs can be built, messages
encrypted with known keys. Agent names are public domain.
Numbers can be guessed, but Nonces cannot be.*}
inductive_set
synth :: "msg set => msg set"
for H :: "msg set"
where
Inj [intro]: "X ∈ H ==> X ∈ synth H"
| Agent [intro]: "Agent agt ∈ synth H"
| Number [intro]: "Number n ∈ synth H"
| Hash [intro]: "X ∈ synth H ==> Hash X ∈ synth H"
| MPair [intro]: "[|X ∈ synth H; Y ∈ synth H|] ==> {|X,Y|} ∈ synth H"
| Crypt [intro]: "[|X ∈ synth H; Key(K) ∈ H|] ==> Crypt K X ∈ synth H"
lemma synth_mono: "G<=H ==> synth(G) <= synth(H)"
apply auto
apply (erule synth.induct)
apply (auto dest: Fst Snd Body)
done
inductive_cases Nonce_synth [elim!]: "Nonce n ∈ synth H"
inductive_cases Key_synth [elim!]: "Key K ∈ synth H"
inductive_cases Hash_synth [elim!]: "Hash X ∈ synth H"
inductive_cases MPair_synth [elim!]: "{|X,Y|} ∈ synth H"
inductive_cases Crypt_synth [elim!]: "Crypt K X ∈ synth H"
inductive_cases Pan_synth [elim!]: "Pan A ∈ synth H"
lemma synth_increasing: "H ⊆ synth(H)"
by blast
subsubsection{*Unions*}
lemma synth_Un: "synth(G) ∪ synth(H) ⊆ synth(G ∪ H)"
by (intro Un_least synth_mono Un_upper1 Un_upper2)
lemma synth_insert: "insert X (synth H) ⊆ synth(insert X H)"
by (blast intro: synth_mono [THEN [2] rev_subsetD])
subsubsection{*Idempotence and transitivity*}
lemma synth_synthD [dest!]: "X∈ synth (synth H) ==> X∈ synth H"
by (erule synth.induct, blast+)
lemma synth_idem: "synth (synth H) = synth H"
by blast
lemma synth_trans: "[| X∈ synth G; G ⊆ synth H |] ==> X∈ synth H"
by (drule synth_mono, blast)
lemma synth_cut: "[| Y∈ synth (insert X H); X∈ synth H |] ==> Y∈ synth H"
by (erule synth_trans, blast)
lemma Agent_synth [simp]: "Agent A ∈ synth H"
by blast
lemma Number_synth [simp]: "Number n ∈ synth H"
by blast
lemma Nonce_synth_eq [simp]: "(Nonce N ∈ synth H) = (Nonce N ∈ H)"
by blast
lemma Key_synth_eq [simp]: "(Key K ∈ synth H) = (Key K ∈ H)"
by blast
lemma Crypt_synth_eq [simp]: "Key K ∉ H ==> (Crypt K X ∈ synth H) = (Crypt K X ∈ H)"
by blast
lemma Pan_synth_eq [simp]: "(Pan A ∈ synth H) = (Pan A ∈ H)"
by blast
lemma keysFor_synth [simp]:
"keysFor (synth H) = keysFor H ∪ invKey`{K. Key K ∈ H}"
by (unfold keysFor_def, blast)
subsubsection{*Combinations of parts, analz and synth*}
lemma parts_synth [simp]: "parts (synth H) = parts H ∪ synth H"
apply (rule equalityI)
apply (rule subsetI)
apply (erule parts.induct)
apply (blast intro: synth_increasing [THEN parts_mono, THEN subsetD]
parts.Fst parts.Snd parts.Body)+
done
lemma analz_analz_Un [simp]: "analz (analz G ∪ H) = analz (G ∪ H)"
apply (intro equalityI analz_subset_cong)+
apply simp_all
done
lemma analz_synth_Un [simp]: "analz (synth G ∪ H) = analz (G ∪ H) ∪ synth G"
apply (rule equalityI)
apply (rule subsetI)
apply (erule analz.induct)
prefer 5 apply (blast intro: analz_mono [THEN [2] rev_subsetD])
apply (blast intro: analz.Fst analz.Snd analz.Decrypt)+
done
lemma analz_synth [simp]: "analz (synth H) = analz H ∪ synth H"
apply (cut_tac H = "{}" in analz_synth_Un)
apply (simp (no_asm_use))
done
subsubsection{*For reasoning about the Fake rule in traces*}
lemma parts_insert_subset_Un: "X∈ G ==> parts(insert X H) ⊆ parts G ∪ parts H"
by (rule subset_trans [OF parts_mono parts_Un_subset2], blast)
lemma Fake_parts_insert: "X ∈ synth (analz H) ==>
parts (insert X H) ⊆ synth (analz H) ∪ parts H"
apply (drule parts_insert_subset_Un)
apply (simp (no_asm_use))
apply blast
done
lemma Fake_parts_insert_in_Un:
"[|Z ∈ parts (insert X H); X: synth (analz H)|]
==> Z ∈ synth (analz H) ∪ parts H";
by (blast dest: Fake_parts_insert [THEN subsetD, dest])
lemma Fake_analz_insert:
"X∈ synth (analz G) ==>
analz (insert X H) ⊆ synth (analz G) ∪ analz (G ∪ H)"
apply (rule subsetI)
apply (subgoal_tac "x ∈ analz (synth (analz G) ∪ H) ")
prefer 2 apply (blast intro: analz_mono [THEN [2] rev_subsetD] analz_mono [THEN synth_mono, THEN [2] rev_subsetD])
apply (simp (no_asm_use))
apply blast
done
lemma analz_conj_parts [simp]:
"(X ∈ analz H & X ∈ parts H) = (X ∈ analz H)"
by (blast intro: analz_subset_parts [THEN subsetD])
lemma analz_disj_parts [simp]:
"(X ∈ analz H | X ∈ parts H) = (X ∈ parts H)"
by (blast intro: analz_subset_parts [THEN subsetD])
lemma MPair_synth_analz [iff]:
"({|X,Y|} ∈ synth (analz H)) =
(X ∈ synth (analz H) & Y ∈ synth (analz H))"
by blast
lemma Crypt_synth_analz:
"[| Key K ∈ analz H; Key (invKey K) ∈ analz H |]
==> (Crypt K X ∈ synth (analz H)) = (X ∈ synth (analz H))"
by blast
lemma Hash_synth_analz [simp]:
"X ∉ synth (analz H)
==> (Hash{|X,Y|} ∈ synth (analz H)) = (Hash{|X,Y|} ∈ analz H)"
by blast
declare parts.Body [rule del]
text{*Rewrites to push in Key and Crypt messages, so that other messages can
be pulled out using the @{text analz_insert} rules*}
lemmas pushKeys [standard] =
insert_commute [of "Key K" "Agent C"]
insert_commute [of "Key K" "Nonce N"]
insert_commute [of "Key K" "Number N"]
insert_commute [of "Key K" "Pan PAN"]
insert_commute [of "Key K" "Hash X"]
insert_commute [of "Key K" "MPair X Y"]
insert_commute [of "Key K" "Crypt X K'"]
lemmas pushCrypts [standard] =
insert_commute [of "Crypt X K" "Agent C"]
insert_commute [of "Crypt X K" "Nonce N"]
insert_commute [of "Crypt X K" "Number N"]
insert_commute [of "Crypt X K" "Pan PAN"]
insert_commute [of "Crypt X K" "Hash X'"]
insert_commute [of "Crypt X K" "MPair X' Y"]
text{*Cannot be added with @{text "[simp]"} -- messages should not always be
re-ordered.*}
lemmas pushes = pushKeys pushCrypts
subsection{*Tactics useful for many protocol proofs*}
ML
{*
structure MessageSET =
struct
(*Prove base case (subgoal i) and simplify others. A typical base case
concerns Crypt K X ∉ Key`shrK`bad and cannot be proved by rewriting
alone.*)
fun prove_simple_subgoals_tac (cs, ss) i =
force_tac (cs, ss addsimps [@{thm image_eq_UN}]) i THEN
ALLGOALS (asm_simp_tac ss)
(*Analysis of Fake cases. Also works for messages that forward unknown parts,
but this application is no longer necessary if analz_insert_eq is used.
Abstraction over i is ESSENTIAL: it delays the dereferencing of claset
DEPENDS UPON "X" REFERRING TO THE FRADULENT MESSAGE *)
(*Apply rules to break down assumptions of the form
Y ∈ parts(insert X H) and Y ∈ analz(insert X H)
*)
val Fake_insert_tac =
dresolve_tac [impOfSubs @{thm Fake_analz_insert},
impOfSubs @{thm Fake_parts_insert}] THEN'
eresolve_tac [asm_rl, @{thm synth.Inj}];
fun Fake_insert_simp_tac ss i =
REPEAT (Fake_insert_tac i) THEN asm_full_simp_tac ss i;
fun atomic_spy_analz_tac (cs,ss) = SELECT_GOAL
(Fake_insert_simp_tac ss 1
THEN
IF_UNSOLVED (Blast.depth_tac
(cs addIs [@{thm analz_insertI},
impOfSubs @{thm analz_subset_parts}]) 4 1))
fun spy_analz_tac (cs,ss) i =
DETERM
(SELECT_GOAL
(EVERY
[ (*push in occurrences of X...*)
(REPEAT o CHANGED)
(res_inst_tac (Simplifier.the_context ss)
[(("x", 1), "X")] (insert_commute RS ssubst) 1),
(*...allowing further simplifications*)
simp_tac ss 1,
REPEAT (FIRSTGOAL (resolve_tac [allI,impI,notI,conjI,iffI])),
DEPTH_SOLVE (atomic_spy_analz_tac (cs,ss) 1)]) i)
end
*}
declare o_def [simp]
lemma Crypt_notin_image_Key [simp]: "Crypt K X ∉ Key ` A"
by auto
lemma Hash_notin_image_Key [simp] :"Hash X ∉ Key ` A"
by auto
lemma synth_analz_mono: "G<=H ==> synth (analz(G)) <= synth (analz(H))"
by (simp add: synth_mono analz_mono)
lemma Fake_analz_eq [simp]:
"X ∈ synth(analz H) ==> synth (analz (insert X H)) = synth (analz H)"
apply (drule Fake_analz_insert[of _ _ "H"])
apply (simp add: synth_increasing[THEN Un_absorb2])
apply (drule synth_mono)
apply (simp add: synth_idem)
apply (blast intro: synth_analz_mono [THEN [2] rev_subsetD])
done
text{*Two generalizations of @{text analz_insert_eq}*}
lemma gen_analz_insert_eq [rule_format]:
"X ∈ analz H ==> ALL G. H ⊆ G --> analz (insert X G) = analz G";
by (blast intro: analz_cut analz_insertI analz_mono [THEN [2] rev_subsetD])
lemma synth_analz_insert_eq [rule_format]:
"X ∈ synth (analz H)
==> ALL G. H ⊆ G --> (Key K ∈ analz (insert X G)) = (Key K ∈ analz G)";
apply (erule synth.induct)
apply (simp_all add: gen_analz_insert_eq subset_trans [OF _ subset_insertI])
done
lemma Fake_parts_sing:
"X ∈ synth (analz H) ==> parts{X} ⊆ synth (analz H) ∪ parts H";
apply (rule subset_trans)
apply (erule_tac [2] Fake_parts_insert)
apply (simp add: parts_mono)
done
lemmas Fake_parts_sing_imp_Un = Fake_parts_sing [THEN [2] rev_subsetD]
method_setup spy_analz = {*
Scan.succeed (fn ctxt =>
SIMPLE_METHOD' (MessageSET.spy_analz_tac (local_clasimpset_of ctxt))) *}
"for proving the Fake case when analz is involved"
method_setup atomic_spy_analz = {*
Scan.succeed (fn ctxt =>
SIMPLE_METHOD' (MessageSET.atomic_spy_analz_tac (local_clasimpset_of ctxt))) *}
"for debugging spy_analz"
method_setup Fake_insert_simp = {*
Scan.succeed (fn ctxt =>
SIMPLE_METHOD' (MessageSET.Fake_insert_simp_tac (local_simpset_of ctxt))) *}
"for debugging spy_analz"
end