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Re: [TLS] Encrypt-then-MAC again (was Re: padding bug)

"Bryan C. Geraghty" <bryan@ravensight.org> Wed, 13 November 2013 21:47 UTC

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From: "Bryan C. Geraghty" <bryan@ravensight.org>
To: mrex@sap.com, 'Ralf Skyper Kaiser' <skyper@thc.org>
References: <CA+BZK2pu1F3zpRJNFX=QjFh=4JkooTgxkjDFPKBosnVCvuSonA@mail.gmail.com> <20131112165343.CA1101AA80@ld9781.wdf.sap.corp>
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Date: Wed, 13 Nov 2013 15:47:49 -0600
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Cc: tls@ietf.org
Subject: Re: [TLS] Encrypt-then-MAC again (was Re: padding bug)
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Martin Rex wrote:

> Ralf Skyper Kaiser wrote:
>> 
>> Encrypt-then-mac has some other security benefits. (Among others that 
>> the decrypt routine never has to process bogus/bad messages [e.g. 
>> those where the MAC would fail in current encrypt-mac].).
> 
> Which benefits are this?
> 
> I am not aware of any security benefit for the real world from doing EtA
over AtE.

Look up "padding oracle attack". Lucky13 is a fairly recent example of a
real-world attack against AtE.
 
Bryan

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