Re: [xmpp] IQ Handling vulnerabilities

"Joe Hildebrand (jhildebr)" <jhildebr@cisco.com> Fri, 14 February 2014 05:27 UTC

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From: "Joe Hildebrand (jhildebr)" <jhildebr@cisco.com>
To: Alexander Holler <holler@ahsoftware.de>, Dave Cridland <dave@cridland.net>
Thread-Topic: [xmpp] IQ Handling vulnerabilities
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Date: Fri, 14 Feb 2014 05:27:30 +0000
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Cc: XMPP Working Group <xmpp@ietf.org>
Subject: Re: [xmpp] IQ Handling vulnerabilities
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(as chair)
Yes, let's call that off-topic.

(as individual)
I don't believe we have to specify an algorithm, since there are no
interoperability consequences.

On 2/11/14 11:48 AM, "Alexander Holler" <holler@ahsoftware.de> wrote:

>Am 11.02.2014 18:59, schrieb Alexander Holler:
>
>> To play with that hash of hash, is it possible that the hash of a hash
>> is the hash itself? If that ever happens your system will have a
>> problem, so how likely is that? And in the proposed solution it's a bit
>> more difficult, because only the higher 5 bytes of the 20 bytes long
>> hash are used. At least for me, the answer to that isn't obvious.
>
>To become completely offtopic, one could formalize that question to how
>the possibility is that
>
>sha1^n(x) = sha1(x) for 2 < n <= 100
>
>(if you need that 100  IDs in series are unique) and furthermore you
>have to look at the upper 5 bytes. I'm not sure if that is what
>cryptographers usually do look at if they check hash algorithms. So
>argueing with whatever they found out about sha1 doesn't look obvious to
>me.
>
>Regards,
>
>Alexander Holler
>
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-- 
Joe Hildebrand