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Re: [dnssd] WGLC on draft-ietf-dnssd-privacy-01

Stephane Bortzmeyer <bortzmeyer@nic.fr> Mon, 26 June 2017 18:43 UTC

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Date: Mon, 26 Jun 2017 20:41:07 +0200
From: Stephane Bortzmeyer <bortzmeyer@nic.fr>
To: Christian Huitema <huitema@huitema.net>
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Subject: Re: [dnssd] WGLC on draft-ietf-dnssd-privacy-01
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On Mon, Jun 26, 2017 at 07:18:19AM -0700,
 Christian Huitema <huitema@huitema.net> wrote 
 a message of 58 lines which said:

> The solution requires that the participating devices have "good
> enough" clocks

Which, IMHO, should be written in the RFC.

> -- to the minute, in practice.

It is not sufficient. The current text says "We will thus use this 24
bit number as nonce, represented as 3 octets." If two machines have
almost perfectly synched clocks, one being at 20:35:44 today, and the
other at 20:35:43, the values won't have the same first 24 bits
(1011001010100010101010000000000 vs. 1011001010100010101001111111111).

There is no obvious solution. We cannot have "fuzzy" comparisons with
nonces.

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