Re: [TLS] Data volume limits

Eric Rescorla <ekr@rtfm.com> Fri, 01 January 2016 19:25 UTC

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From: Eric Rescorla <ekr@rtfm.com>
Date: Fri, 1 Jan 2016 11:24:27 -0800
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To: James Cloos <cloos@jhcloos.com>
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Subject: Re: [TLS] Data volume limits
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On Fri, Jan 1, 2016 at 11:00 AM, James Cloos <cloos@jhcloos.com> wrote:

> [Msg for followup picked at random from this thread -JimC]
>
> One thing we should remember on this thread is that it does not only
> apply to aes and its' 128-bit block size.
>
> Because TLS chose to create a NotQuiteChaCha rather than use ChaCha,
> its chacha20poly1305 also has a small data volume limit (2^40 bits;
> only twice aesgcm's limit).
>

Can you elaborate on this point a bit? I haven't been focusing on ChaCha,
but we're not quite done with ChaCha yet, so if changes are needed, now
would be
the time.

-Ekr


> So key updates or re-keying will be more universally required.
>
> (Are there any aeads currently spec'ed with both large enough blocks and
> large enough nonces safely to avoid key updates?)
>
> -JimC
> --
> James Cloos <cloos@jhcloos.com>         OpenPGP: 0x997A9F17ED7DAEA6
>
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