Re: [TLS] New cipher suites for SRP

Jeffrey Walton <noloader@gmail.com> Mon, 20 July 2015 12:15 UTC

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Date: Mon, 20 Jul 2015 08:15:05 -0400
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From: Jeffrey Walton <noloader@gmail.com>
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Subject: Re: [TLS] New cipher suites for SRP
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>>This is possible, but you’d need to have the client and server negotiate
> based on
>>what they have.  For example, if the server has a SRP verifier from the
> current
>>protocol, but the client has a stored PBKDF2 hash of the password for that
> server,
>>they cannot communicate and would need to pick a different cipher suite.  I
> am not
>>sure how you can do this without revealing the existence of an account
> under some
>>circumstances.  So this might be a situation where fewer protocol options
> is better.
>
> Of course both sides have to agree on  common protocol details: You could do
> this by specifying that you want to use PAKE and refine in an extension a
> set of schemes that you are capable of.

There's not much to negotiate. I would expend minimal energy on
negotiating parameters. The server holds the verifiers, and they are
set in stone. To get a verifier, the user needs to be pre-provisioned.

Spend energy on keeping the identity private.

If you want to go something cool, add an OTP as a second factor. There
are two ways to do it based on the math around the verifiers (that I
am aware). I have implementations for both in Crypto++, if interested.

Jeff