Subject: RE: [TLS] NIST TLS recomendations (IV generation)

From: "Blumenthal, Uri" <[email-masked]>
Date: Tue, 21 Nov 2006 13:04:55 -0500

>Being unpredictable makes the IVs unique except with 
>negligible probability (unless you've used CBC on too 
>long a data stream), so there's no need for an explicit 
>uniqueness requirement.

It's that small probability that bothers me. But I guess it is small
enough to ignore for practical purposes of real-world commercial
applications.

>If we write "MUST be unique", this might evoke the perception 
>that implementations using randomly generated IVs are expected 
>to check whether these actually are unique, which usually is 
>totally impractical, and totally unnecessary.

Agree.

>So "SHOULD be chosen at random, and MUST be unpredictable" 
>looks exactly right to me.

OK.

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