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

"Blumenthal, Uri - 0662 - MITLL" <uri@ll.mit.edu> Fri, 27 November 2009 13:32 UTC

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From: "Blumenthal, Uri - 0662 - MITLL" <uri@ll.mit.edu>
To: "'nelson@bolyard.me'" <nelson@bolyard.me>
Date: Fri, 27 Nov 2009 08:31:56 -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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Again, a very good point! I agree.


----- Original Message -----
From: Nelson B Bolyard <nelson@bolyard.me>
To: Blumenthal, Uri - 0662 - MITLL
Cc: tls@ietf.org <tls@ietf.org>
Sent: Fri Nov 27 00:21:11 2009
Subject: Re: [TLS] Quest for Unified Solution to TLS Renegotiation

On 2009-11-26 08:04 PST, 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?).

Yes.  In Hardware Security Modules that pass certain FIPS security levels,
and implement the PRF in hardware, a change to the use of the PRF that
causes data (non-key material) to get combined with key material (the master
secret) would require introduction of new paths, a big change, would take
at least a year to get all the approvals.

If you want to change inputs to the PRF, just keep keys separate from
non-key data.  Combine new non-key data with other existing non-key data
inputs, not with key data inputs.

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