src/HOL/Auth/Yahalom_Bad.thy

 Demonstrates of why Oops is necessary.  This protocol can be attacked because
 it doesn't keep NB secret, but without Oops it can be "verified" anyway.
 The issues are discussed in lcp's LICS 2000 invited lecture.
 *}
 
-consts  yahalom   :: "event list set"
-inductive "yahalom"
-  intros
+inductive_set yahalom :: "event list set"
+  where
          (*Initial trace is empty*)
    Nil:  "[] \<in> yahalom"
 
          (*The spy MAY say anything he CAN say.  We do not expect him to
            invent new nonces here, but he can also use NS1.  Common to
            all similar protocols.*)
-   Fake: "[| evsf \<in> yahalom;  X \<in> synth (analz (knows Spy evsf)) |]
+ | Fake: "[| evsf \<in> yahalom;  X \<in> synth (analz (knows Spy evsf)) |]
           ==> Says Spy B X  # evsf \<in> yahalom"
 
          (*A message that has been sent can be received by the
            intended recipient.*)
-   Reception: "[| evsr \<in> yahalom;  Says A B X \<in> set evsr |]
+ | Reception: "[| evsr \<in> yahalom;  Says A B X \<in> set evsr |]
                ==> Gets B X # evsr \<in> yahalom"
 
          (*Alice initiates a protocol run*)
-   YM1:  "[| evs1 \<in> yahalom;  Nonce NA \<notin> used evs1 |]
+ | YM1:  "[| evs1 \<in> yahalom;  Nonce NA \<notin> used evs1 |]
           ==> Says A B {|Agent A, Nonce NA|} # evs1 \<in> yahalom"
 
          (*Bob's response to Alice's message.*)
-   YM2:  "[| evs2 \<in> yahalom;  Nonce NB \<notin> used evs2;
+ | YM2:  "[| evs2 \<in> yahalom;  Nonce NB \<notin> used evs2;
              Gets B {|Agent A, Nonce NA|} \<in> set evs2 |]
           ==> Says B Server
                   {|Agent B, Nonce NB, Crypt (shrK B) {|Agent A, Nonce NA|}|}
                 # evs2 \<in> yahalom"
 
          (*The Server receives Bob's message.  He responds by sending a
             new session key to Alice, with a packet for forwarding to Bob.*)
-   YM3:  "[| evs3 \<in> yahalom;  Key KAB \<notin> used evs3;  KAB \<in> symKeys;
+ | YM3:  "[| evs3 \<in> yahalom;  Key KAB \<notin> used evs3;  KAB \<in> symKeys;
              Gets Server
                   {|Agent B, Nonce NB, Crypt (shrK B) {|Agent A, Nonce NA|}|}
                \<in> set evs3 |]
           ==> Says Server A
                    {|Crypt (shrK A) {|Agent B, Key KAB, Nonce NA, Nonce NB|},

                 # evs3 \<in> yahalom"
 
          (*Alice receives the Server's (?) message, checks her Nonce, and
            uses the new session key to send Bob his Nonce.  The premise
            A \<noteq> Server is needed to prove Says_Server_not_range.*)
-   YM4:  "[| evs4 \<in> yahalom;  A \<noteq> Server;  K \<in> symKeys;
+ | YM4:  "[| evs4 \<in> yahalom;  A \<noteq> Server;  K \<in> symKeys;
              Gets A {|Crypt(shrK A) {|Agent B, Key K, Nonce NA, Nonce NB|}, X|}
                 \<in> set evs4;
              Says A B {|Agent A, Nonce NA|} \<in> set evs4 |]
           ==> Says A B {|X, Crypt K (Nonce NB)|} # evs4 \<in> yahalom"