X-Git-Url: https://git.distorted.org.uk/~mdw/secnet/blobdiff_plain/1e80c220a810380ae8b5a155e2bd6937c951c83c..0a6cbadea08d824e26838a18bb75745c78f27461:/NOTES

diff --git a/NOTES b/NOTES
index 6a245ec..3e9d71d 100644
--- a/NOTES
+++ b/NOTES
@@ -174,8 +174,9 @@ quite stable so the feature doesn't gain us much.
 
 Definitions:
 
-A is the originating gateway machine
-B is the destination gateway machine
+A is the originating gateway machine name
+B is the destination gateway machine name
+A+ and B+ are the names with optional additional data, currently ignored
 PK_A is the public RSA key of A
 PK_B is the public RSA key of B
 PK_A^-1 is the private RSA key of A
@@ -193,21 +194,21 @@ i? is appropriate index for receiver
 Note that 'i' may be re-used from one session to the next, whereas 'n'
 is always fresh.
 
-The protocol version selection stuff is not yet implemented: I'm not
-yet convinced it's a good idea.  Instead, the initiator could try
-using its preferred protocol (which starts with a different magic
-number) and fall back if there's no reply.
+The protocol version selection stuff is not yet implemented.
 
 Messages:
 
-1) A->B: *,iA,msg1,A,B,protorange-A,nA
+1) A->B: *,iA,msg1,A+,B+,nA
 
-2) B->A: iA,iB,msg2,B,A,chosen-protocol,nB,nA
+i* must be encoded as 0.  (However, it is permitted for a site to use
+zero as its "index" for another site.)
+
+2) B->A: iA,iB,msg2,B+,A+,nB,nA
 
 (The order of B and A reverses in alternate messages so that the same
 code can be used to construct them...)
 
-3) A->B: {iB,iA,msg3,A,B,protorange-A,chosen-protocol,nA,nB,g^x mod m}_PK_A^-1
+3) A->B: {iB,iA,msg3,A+,B+,nA,nB,g^x mod m}_PK_A^-1
 
 If message 1 was a replay then A will not generate message 3, because
 it doesn't recognise nA.
@@ -215,18 +216,11 @@ it doesn't recognise nA.
 If message 2 was from an attacker then B will not generate message 4,
 because it doesn't recognise nB.
 
-If an attacker is trying to manipulate the chosen protocol, B can spot
-this when it sees A's message 3.
-
-4) B->A: {iA,iB,msg4,B,A,protorange-B,chosen-protocol,nB,nA,g^y mod m}_PK_B^-1
+4) B->A: {iA,iB,msg4,B+,A+,nB,nA,g^y mod m}_PK_B^-1
 
 At this point, A and B share a key, k. B must keep retransmitting
 message 4 until it receives a packet encrypted using key k.
 
-A can abandon the exchange if the chosen protocol is not the one that
-it would have chosen knowing the acceptable protocol ranges of A and
-B.
-
 5) A: iB,iA,msg5,(ping/msg5)_k
 
 6) B: iA,iB,msg6,(pong/msg6)_k
@@ -251,10 +245,6 @@ some reason.
 
 8) i?,i?,msg0,(send-packet/msg9,packet)_k
 
-Some messages may take a long time to prepare (software modexp on slow
-machines); this is a "please wait" message to indicate that a message
-is in preparation.
-
 **** Other messages
 
 9) i?,i?,NAK (NAK is encoded as zero)