# HG changeset patch
# User paulson
# Date 840559997 -7200
# Node ID cdf9bcd53749584da8806a19579ff07b95f7a172
# Parent  f0839bab4b00cb09e550ec3d2c3547bf02160d86
Working version of NS, messages 1-4!

diff -r f0839bab4b00 -r cdf9bcd53749 src/HOL/Auth/Event.ML
--- a/src/HOL/Auth/Event.ML	Tue Aug 20 17:46:24 1996 +0200
+++ b/src/HOL/Auth/Event.ML	Tue Aug 20 18:53:17 1996 +0200
@@ -384,14 +384,22 @@
 be traces.induct 1;
 bd NS3_msg_in_parts_sees_Enemy 5;
 by (ALLGOALS Asm_simp_tac);
-by (ALLGOALS
-    (best_tac 
+(*NS1 and NS2*)
+map (by o fast_tac (!claset addDs [Suc_leD] addss (!simpset))) [3,2];
+(*Fake and NS3*)
+map (by o best_tac
      (!claset addSDs [newK_invKey]
 	      addDs [impOfSubs (analz_subset_parts RS keysFor_mono),
 		     impOfSubs (parts_insert_subset_Un RS keysFor_mono),
 		     Suc_leD]
 	      addEs [new_keys_not_seen RS not_parts_not_analz RSN (2,rev_notE)]
-	      addss (!simpset))));
+	      addss (!simpset)))
+    [2,1];
+(*NS4*)
+by (step_tac (!claset addSDs [Suc_leD, newK_invKey]) 1);
+by (deepen_tac (!claset addIs [impOfSubs keysFor_mono]) 0 2);
+by (fast_tac (!claset addDs [Says_imp_old_keys]
+	              addss (!simpset addsimps [le_def])) 1);
 val lemma = result();
 
 goal thy 
@@ -526,6 +534,7 @@
 by (auto_tac (!claset addIs [Says_imp_old_keys], !simpset));
 qed "Says_S_message_form";
 
+(*Currently unused.  Needed only to reason about the VERY LAST message.*)
 goal thy 
  "!!evs. [| evs = Says S A (Crypt {|Nonce NA, Agent B, Key K, X|}   \
 \                           (serverKey A)) # evs';                  \
@@ -540,7 +549,6 @@
 
 
 
-
 (****
  The following is to prove theorems of the form
 
@@ -568,6 +576,7 @@
 		      addDs [impOfSubs analz_subset_parts,
                              impOfSubs parts_insert_subset_Un]
                       addss (!simpset)) 1);
+by (fast_tac (!claset addss (!simpset)) 1);
 result();
 
 
diff -r f0839bab4b00 -r cdf9bcd53749 src/HOL/Auth/Event.thy
--- a/src/HOL/Auth/Event.thy	Tue Aug 20 17:46:24 1996 +0200
+++ b/src/HOL/Auth/Event.thy	Tue Aug 20 18:53:17 1996 +0200
@@ -85,24 +85,27 @@
 (*NS3 DOESN'T ALLOW INTERLEAVING -- that is, it only responds to the
   MOST RECENT message.*)
 
+(*Needham-Schroeder Shared-Key protocol (from BAN paper, page 247)*)
 consts  traces   :: "event list set"
 inductive traces
   intrs 
+         (*Initial trace is empty*)
     Nil  "[]: traces"
 
-    (*The enemy MAY say anything he CAN say.  We do not expect him to
-      invent new nonces here, but he can also use NS1.*)
-    Fake "[| evs: traces;  B ~= Enemy;  
-             X: synth(analz(sees Enemy evs))
+         (*The enemy 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 "[| evs: traces;  B ~= Enemy;  X: synth (analz (sees Enemy evs))
           |] ==> (Says Enemy B X) # evs : traces"
 
+         (*Alice initiates a protocol run*)
     NS1  "[| evs: traces;  A ~= Server
           |] ==> (Says A Server {|Agent A, Agent B, Nonce (newN evs)|}) 
                  # evs : traces"
 
-          (*We can't trust the sender field, hence the A' in it.
-            This allows the Server to respond more than once to A's
-            request...*)
+         (*Server's response to Alice's message.
+           !! It may respond more than once to A's request !!
+	   We can't trust the sender field, hence the A' in it.*)
     NS2  "[| evs: traces;  A ~= B;  A ~= Server;
              (Says A' Server {|Agent A, Agent B, Nonce NA|}) : set_of_list evs
           |] ==> (Says Server A 
@@ -110,9 +113,9 @@
                            (Crypt {|Key (newK evs), Agent A|} (serverKey B))|}
                    (serverKey A))) # evs : traces"
 
-           (*We can't assume S=Server.  Agent A "remembers" her nonce.
-             May assume WLOG that she is NOT the Enemy: the Fake rule
-             covers this case.  Can inductively show A ~= Server*)
+          (*We can't assume S=Server.  Agent A "remembers" her nonce.
+            May assume WLOG that she is NOT the Enemy: the Fake rule
+            covers this case.  Can inductively show A ~= Server*)
     NS3  "[| evs: traces;  A ~= B;
              (Says S A (Crypt {|Nonce NA, Agent B, Key K, X|} (serverKey A))) 
                : set_of_list evs;
@@ -120,12 +123,8 @@
              (Says A Server {|Agent A, Agent B, Nonce NA|}) : set_of_list evs
           |] ==> (Says A B X) # evs : traces"
 
-(*Initial version of NS2 had 
-
-        {|Agent A, Agent B, Key (newK evs), Nonce NA|}
-
-  for the encrypted part; the version above is LESS explicit, hence
-  HARDER to prove.  Also it is precisely as in the BAN paper.
-*)
-
+    NS4  "[| evs: traces;  A ~= B;  
+             (Says A' B (Crypt {|Key K, Agent A|} (serverKey B))) 
+               : set_of_list evs
+          |] ==> (Says B A (Crypt (Nonce (newN evs)) K)) # evs : traces"
 end