Re: #612: 9.2.2 and ALPN

On Tue, Nov 11, 2014 at 6:03 PM, Mark Nottingham <mnot@mnot.net> wrote:
> Not explicit here but implied (and seemingly not controversial) were #1 (making all cipher suite requirements specific to TLS 1.2), #3 (keep the required interop suite as mandatory to deploy) and #4 (Clarify that cipher suite requirements apply to deployments, not impl).

To clarify #3 and #4: If a server only has an ECDSA certificate, then
it shouldn't be required to (and in fact, cannot) implement
TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256. I believe that
TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256 should be mandatory if the
certificate is RSA and TLS_ECDHE_ECDSA_WITH_AES_128_GCM_SHA256 if the
certificate is ECDSA, because that is implying that having an RSA
certificate is mandatory, and that's not good. Also, as a practical
matter, in a few years it is likely to be the case that
TLS_ECDHE_ECDSA_WITH_AES_128_GCM_SHA256 is the most interoperable
cipher suite for servers to support, because Windows 7's SChannel
supports it, but Windows 7's SChannel does not support
TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256. And, in practice, all browsers
that support TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256 also support
TLS_ECDHE_ECDSA_WITH_AES_128_GCM_SHA256.

Cheers,
Brian

Received on Wednesday, 12 November 2014 02:39:03 UTC