Re: [hiprg] HIP DEX suggestion

Robert Moskowitz <rgm@htt-consult.com> Thu, 04 August 2011 14:28 UTC

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Date: Thu, 04 Aug 2011 10:28:06 -0400
From: Robert Moskowitz <rgm@htt-consult.com>
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To: Ed Beroset <beroset@mindspring.com>
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Subject: Re: [hiprg] HIP DEX suggestion
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On 08/04/2011 09:20 AM, Ed Beroset wrote:
> Speaking of implementations, I have a suggestion about HIP DEX. Right now it specifies the use of AES-CBC but I would like to see if we could change that to either AES-CFB or AES-CTR.  The reason is that for CBC, one must implement both the AES encrypt and decrypt functions.  With CFB and CTR, one only need implement AES encrypt.  This saves about 1.5k of code space on a typical small microprocessor for which HIP DEX is intended and has at least equivalent (and some say better) security properties.

Very good point.  Plus hardware that does AES-CCM should be able to do 
CTR 'easily'. But I have to look at what the counter would be.  CBC was 
'easy' in that there was a natural nonce.