Yes. I agree that SCSV could be defined to convey only 1 bit of information while RI conveys 2 bits, and agree that -01 (which went through last call) does not define it that way. What I don't understand is why the issue of changing the semantics of -01 and -03 to reflect a "1 bit SCSV" is so #$%& important. 1. It is trivially easy to code to either version. 2. There is no security impact of using either version. 3. It is easier to articulate and to understand an "identical" soundbite than to explain how SCSV and empty RI are semantically different, and 4. The "identical" version is ready to go, in the form of -03 that can be published as an RFC right now. And although I hesitate to bring up the following since they are non-essential, 5. SCSV is a hack meant to appease ancient and/or non-conforming servers. That is one ugly baby, and I wish it would just disappear. There is absolutely no reason for it ever to be sent in a ClientHello containing a non-empty RI (it is a no-op that just wastes N bits of bandwidth to convey 0 bits of additional information, and no legacy implementation would ever send or interpret it), so I see absolutely no downside to prohibiting it during renegotiation. 6. Reducing optional elements is always good security hygiene (hash collision space, covert channels, stack overflow alignment, etc.) Take away a useless knob and nobody can twiddle that knob against you. Dave -----Original Message----- From: Martin Rex [mailto:mrex@xxxxxxx] Sent: Tuesday, January 26, 2010 4:44 PM To: Kemp, David P. Cc: tls@xxxxxxxx; ietf@xxxxxxxx Subject: Re: [TLS] Confirming consensus about one Kemp, David P. wrote: > > Rationale: > > Version -01 states that the semantics of SCSV is identical to the > semantics an empty RI, namely: "this client is capable of supporting > secure renegotiation, and this ClientHello message is an initial > handshake, not a renegotiation handshake." But you do realize that we discussed this issue on the WG mailing list and the I provided an explanation along the lines of a semi-formal correctness proof that this rationale is based on a misunderstanding and a poor choice of words in the specification. http://www.ietf.org/mail-archive/web/tls/current/msg05466.html -Martin _______________________________________________ Ietf mailing list Ietf@xxxxxxxx https://www.ietf.org/mailman/listinfo/ietf