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Re: [TLS] [Cfrg] Closing out tls1.3 "Limits on key usage" PRs (#765/#769).

Hal Murray <hmurray@megapathdsl.net> Fri, 03 March 2017 01:54 UTC

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To: Andrey Jivsov <crypto@brainhub.org>
From: Hal Murray <hmurray@megapathdsl.net>
In-Reply-To: Message from Andrey Jivsov <crypto@brainhub.org> of "Thu, 02 Mar 2017 15:15:28 PST." <cd2835c7-d093-60b0-df9c-998d77a6a26e@brainhub.org>
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Date: Thu, 02 Mar 2017 17:54:18 -0800
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Subject: Re: [TLS] [Cfrg] Closing out tls1.3 "Limits on key usage" PRs (#765/#769).
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crypto@brainhub.org said:
> I also think that counting in blocks is cleaner. Counting in bytes is a
> close alternative. 

Does counting bytes work?  If the real limit is blocks, I think you will have 
to round up the byte count when you send a partial block.

If re-keying too often isn't too expensive, you could get a safe answer by 
counting bytes and assuming that every byte went in a separate block.

You might want to round down many more orders of magnitude so the re-key code 
gets exercised often enough.  Or maybe provide a back door to set the limit 
so that path can be tested with reasonable resources.

-- 
These are my opinions.  I hate spam.

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