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Re: [TLS] Cipher suite values to indicate TLS capability

Chris Richardson <chris@randomnonce.org> Wed, 06 June 2012 01:11 UTC

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Date: Tue, 05 Jun 2012 21:11:22 -0400
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From: Chris Richardson <chris@randomnonce.org>
To: Adam Langley <agl@google.com>
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Cc: tls@ietf.org
Subject: Re: [TLS] Cipher suite values to indicate TLS capability
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On Tue, Jun 5, 2012 at 4:39 PM, Adam Langley <agl@google.com> wrote:
> However, with the downgrade to SSLv3 we loose an important security
> feature: ECDHE.
...
> So I'd like to introduce TLS_CAPABLE_SCSV (0x00fe) in SSLv3
> handshakes. TLS_EMPTY_RENEGOTIATION_INFO_SCSV has shown that we can
> deploy new ciphersuites for SSLv3 and the semantics of
> TLS_CAPABLE_SCSV would be that servers would reject any SSLv3
> handshakes that included this ciphersuite with a fatal error.

Thinking through various scenarios... if I'm a TLS-capable server that
does not support foward-secure cipher suites, what reason would I have
any reason to reject an SSLv3 hello containing the TLS_CAPABLE_SCSV?

 -- Chris

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