Re: [TLS] Last Call: draft-hoffman-tls-additional-random-ext (Additional Random

Nicolas Williams <> Mon, 26 April 2010 21:38 UTC

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Date: Mon, 26 Apr 2010 16:36:34 -0500
From: Nicolas Williams <>
To: Marsh Ray <>, Paul Hoffman <>
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Subject: Re: [TLS] Last Call: draft-hoffman-tls-additional-random-ext (Additional Random
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On Mon, Apr 26, 2010 at 04:18:33PM -0500, Marsh Ray wrote:
> Taking off of CC list as this seems to be very TLS specific.

This is an IETF LC, not a WG LC; IETF LC comments should be sent to  If anything, we might want to drop

> On 4/26/2010 3:38 PM, Nicolas Williams wrote:
> > How is the sub-thread on RNGs and PRNGs relevant here?
> The draft was said to strengthen some properties of the protocol,
> particularly entropy in the RNG. In order to evaluate the draft, we need
> to agree on what those properties are supposed to be and how they affect
> the different protocol structures.

By analogy to legal review, if we don't need to reach the issue, then we
don't need to discuss it.

RNG/PRNG matters either apply, in which case we can might in, or they
don't.  I believe it is correct to assert that we don't need to discuss
[P]PRNGs in detail, or even at all if we agree that the existing TLS
client_random and server_random fields are sufficient.

Thus ISTM that we should first consider either whether the client_random
and server_random fields are sufficient _assuming_ compliant [P]RNGs or
consider how draft-hoffman-tls-additional-random-ext can ameliorate TLS
implementations that have poor [P]RNGs.

Ah!  Perhaps what's happening here is that Paul intends for the
additional random inputs to be provided by the _application_, from
outside the TLS implementation.  In that case an application could make
secure use of TLS even when the underlying TLS implementation has a poor
[P]RNG.  That would make draft-hoffman-tls-additional-random-ext much
more interesting (combined with some editing I'd drop my objections).