[PATCH 07/25] NOTES: Remove unimplemented protocol negotiation

Ian Jackson ijackson at chiark.greenend.org.uk
Sat Jul 20 00:38:51 BST 2013

The protocol negotiation mechanism documented in NOTES is not
implemented.  Remove it from the document.

Signed-off-by: Ian Jackson <ijackson at chiark.greenend.org.uk>
 NOTES |   20 +++++---------------
 1 files changed, 5 insertions(+), 15 deletions(-)

diff --git a/NOTES b/NOTES
index 09c083e..33c010e 100644
--- a/NOTES
+++ b/NOTES
@@ -193,21 +193,18 @@ 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.
-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
+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 +212,11 @@ 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
 5) A: iB,iA,msg5,(ping/msg5)_k
 6) B: iA,iB,msg6,(pong/msg6)_k

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