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Re: [TLS] Dumb thoughts for hardware backed keys for AEAD

Bill Cox <waywardgeek@google.com> Tue, 01 December 2015 03:17 UTC

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Date: Mon, 30 Nov 2015 19:17:36 -0800
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From: Bill Cox <waywardgeek@google.com>
To: Eric Rescorla <ekr@rtfm.com>
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Subject: Re: [TLS] Dumb thoughts for hardware backed keys for AEAD
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On Mon, Nov 30, 2015 at 7:06 PM, Eric Rescorla <ekr@rtfm.com> wrote:

> Hi Bill,
>
> I am sorry, but I do not understand what you are proposing. Do you think
> you could try restating the computation you have in mind, perhaps by
> providing an equation that explains the construct?
>

Sure.  I'll stick to HMAC, which is more widely understood.  We do
encrypt-them-mac using the write key.  The inner SHA-256 consumes the
entire ciphertext, and at the end, the outer SHA-256 is applied.

This hack would use a different key for the outer SHA-256.  This way, it is
only used to hash a single block.

Quite a hack, right :)

Bill

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