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Re: [TLS] Quest for Unified Solution to TLS Renegotiation

"Blumenthal, Uri - 0662 - MITLL" <uri@ll.mit.edu> Thu, 26 November 2009 18:12 UTC

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From: "Blumenthal, Uri - 0662 - MITLL" <uri@ll.mit.edu>
To: "tls@ietf.org" <tls@ietf.org>
Date: Thu, 26 Nov 2009 13:11:35 -0500
Thread-Topic: [TLS] Quest for Unified Solution to TLS Renegotiation
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Subject: Re: [TLS] Quest for Unified Solution to TLS Renegotiation
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I forgot about that. Good point. I agree.

As for SSLv3 - SMNP (Simply Not My Problem :). Would be nice to address it
as well, but I'd rather not bend over backwards to also fix SSLv3.

On 11/26/09  12:23 , "David-Sarah Hopwood" <david-sarah@jacaranda.org>
wrote:
> Blumenthal, Uri - 0662 - MITLL wrote:
>> Yes, previous_verify_data MUST be a part of the input to the PRF. What Yoav
>> Nir said (XOR-ing it with the master_secret), should work (out of hand -
>> anybody sees a problem with it?).
> 
> The previous_verify_data is not necessarily secret, so this requires the
> PRF to be secure against related-key attack. The particular PRFs used in
> SSLv3 and TLS 1.0 to 1.2 should be secure in that sense, but (if we
> decide to use this approach) I still prefer what I suggested before:
> 
>     verify_data =
>       PRF(master_secret, finished_label, Hash(handshake_messages)
>                                          + previous_verify_data)
>         [0..verify_data_length-1];
> 
> which uses the PRF in a more conventional way.
-- 
Regards,
Uri         uri@ll.mit.edu
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