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Re: [AVTCORE] FYI: draft-rescorla-random-cname-00

Eric Rescorla <ekr@rtfm.com> Wed, 11 July 2012 14:51 UTC

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From: Eric Rescorla <ekr@rtfm.com>
Date: Wed, 11 Jul 2012 07:51:24 -0700
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To: Colin Perkins <csp@csperkins.org>
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Cc: IETF AVTCore WG <avt@ietf.org>
Subject: Re: [AVTCORE] FYI: draft-rescorla-random-cname-00
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On Wed, Jul 11, 2012 at 5:00 AM, Colin Perkins <csp@csperkins.org> wrote:
> [limiting replies to avt, since this is about details]
>
> On 9 Jul 2012, at 20:24, Eric Rescorla wrote:
>> As discussed at the RTCWEB interim:
>>
>> Executive summary: use a CSPRNG to generate CNAMEs.
>
>
> Section 2.1 says: "The timestamp (from the RTP header) to within a few seconds.  With a typical 100 ticks/second clock, this represents about 10 bits of entropy at most (and potentially more like 2-3 bits)". The RTP timestamp has a random initial value, and typically ticks at either 8kHz or 90kHz. It's not a wall clock. There's more entropy here than supposed.

Sorry, RTCP NTP timestamp.

-Ekr

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