Re: [TLS] [perpass] Let's remove gmt_unix_time from TLS

Peter Gutmann <pgut001@cs.auckland.ac.nz> Thu, 12 September 2013 11:25 UTC

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From: Peter Gutmann <pgut001@cs.auckland.ac.nz>
To: Stephen Farrell <stephen.farrell@cs.tcd.ie>, Nick Mathewson <nickm@torproject.org>, "mrex@sap.com" <mrex@sap.com>, "perpass@ietf.org" <perpass@ietf.org>, "tls@ietf.org" <tls@ietf.org>
Thread-Topic: [TLS] [perpass] Let's remove gmt_unix_time from TLS
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Date: Thu, 12 Sep 2013 11:24:48 +0000
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Subject: Re: [TLS] [perpass] Let's remove gmt_unix_time from TLS
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Stephen Farrell <stephen.farrell@cs.tcd.ie>; writes:

>(And that's a common pattern actually: someone says "if we do X that'll make
>privacy a bit better" and someone else says "but there are so many other ways
>to leak private info, why bother just doing X?")

I've only partially seen it as a privacy issue but more as a security issue,
by telling an attacker that your clock is two weeks out you're letting them
know that they can reuse an expired cert or replay an old CRL.  Even in terms
of privacy it wasn't a specific user-tracking thing but more a question of why
you needed to tell the world what your system clock was set to.  So my code
has always populated the field with random noise, not an actual time.

Peter.