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Re: [Cfrg] [jose] Question from JOSE working group

"Weger, B.M.M. de" <b.m.m.d.weger@TUE.nl> Mon, 02 July 2012 22:19 UTC

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From: "Weger, B.M.M. de" <b.m.m.d.weger@TUE.nl>
To: John Bradley <ve7jtb@ve7jtb.com>, "Richard L. Barnes" <rbarnes@bbn.com>
Date: Tue, 03 Jul 2012 00:19:20 +0200
Thread-Topic: [Cfrg] [jose] Question from JOSE working group
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Cc: "cfrg@irtf.org" <cfrg@irtf.org>, "jose@ietf.org" <jose@ietf.org>
Subject: Re: [Cfrg] [jose] Question from JOSE working group
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Hi John,

> Chosen-prefix attacks require the text of both messages to be the same up
> to the point where the attacker can insert the collision function blocks.

Correction: 
It's identical-prefix attacks that require the text of both messages to be 
the same up to the point where the attacker can insert the collision blocks.
That's exactly why these attacks are called "identical-prefix".

Chosen-prefix attacks allow the attacker to choose whatever he wants in
each of the two messages up to the point where ... etc.

Chosen-prefix attacks fail if the attacker has no sufficient control over / 
cannot sufficiently predict this part of the messages.

Grtz,
Benne de Weger

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