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Re: [TLS] Call for acceptance of draft-moeller-tls-downgrade-scsv

Rob Stradling <rob.stradling@comodo.com> Thu, 23 January 2014 21:03 UTC

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Date: Thu, 23 Jan 2014 21:03:08 +0000
From: Rob Stradling <rob.stradling@comodo.com>
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To: Adam Langley <agl@google.com>
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Subject: Re: [TLS] Call for acceptance of draft-moeller-tls-downgrade-scsv
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On 23/01/14 20:43, Adam Langley wrote:
>> I guess the chances of a server actually having TLS_NULL_WITH_NULL_NULL
>> enabled and choosing to select it above all other mutually supported ciphers
>> is pretty remote.  But nonetheless, is there any reason why
>> TLS_FALLBACK_SCSV couldn't have a value of, say, {0x00, 0xFE} ?
>
> Has anything ever implemented TLS_NULL_WITH_NULL_NULL?

A quick Google search suggests Yes.

> Either way, it's not a big problem to change the SCSV value if need
> be, although I don't believe that servers mistaking it for
> TLS_NULL_WITH_NULL_NULL will be an issue.

OK.

> Additionally, the value is added at the end of the list in practice.

How about stating this "in practice" behaviour as a MUST or SHOULD 
requirement in the draft?

-- 
Rob Stradling
Senior Research & Development Scientist
COMODO - Creating Trust Online

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