Re: [TLS] draft-rescorla-tls-subcerts

Kyle Rose <krose@krose.org> Fri, 08 July 2016 00:08 UTC

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From: Kyle Rose <krose@krose.org>
Date: Thu, 7 Jul 2016 20:08:11 -0400
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To: Ilari Liusvaara <ilariliusvaara@welho.com>
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Subject: Re: [TLS] draft-rescorla-tls-subcerts
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On Thu, Jul 7, 2016 at 6:13 PM, Ilari Liusvaara <ilariliusvaara@welho.com>
wrote:

>
> I also checked if one could do some funky stuff with credential lifetime
> notation to limit the lifetime. Nothing came up (apart for using 16-bit
> count in decaseconds (das) only allowing presenting lifetimes up to 7
> days, 14 hours, 2 minutes and 30 seconds). :->
>

What would it be anchored to if it's not an absolute time? If you anchor
the interval to, say, the issue time of the end-entity cert you haven't
limited the resolution of the interval in any useful way: it still needs to
be able to express intervals that end at or after the expire time. I
suppose an implementor could be less likely to screw up if you also include
and sign the interval start and require two things:

(1) interval start <= now() + fuzz
(2) interval length < 7 days

Are these really much easier than

(1) interval start <= now() +- fuzz <= interval end
(2) interval end - interval start < 7 days

?

Kyle