Re: [TLS] AAED ciphers: AES-GCM vs AES-EAX/AES-CCM: a meta-analysis

mrex@sap.com (Martin Rex) Sat, 24 January 2015 05:14 UTC

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To: Tom Ritter <tom@ritter.vg>
Date: Sat, 24 Jan 2015 06:14:44 +0100 (CET)
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From: mrex@sap.com (Martin Rex)
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Subject: Re: [TLS] AAED ciphers: AES-GCM vs AES-EAX/AES-CCM: a meta-analysis
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Tom Ritter wrote:
> "Martin Thomson" <martin.thomson@gmail.com>; wrote:
>>
>> Michael Clark <michael@metaparadigm.com>; wrote:
>>>
>>> Interesting. Should draft-pironti-tls-length-hiding-01 be added to
>>> Related Active Documents (not working group documents) section
>>
>> That's an automatically generated list.  I suspect the reason that it
>> doesn't appear is that it is presently expired.
> 
> Something I feel very bad about. I am a big proponent of making length
> hiding possible in 1.3 and need to find time to put more effort into this.
> I encourage the chairs or WG to bug me if they don't see anything about
> this in a timeframe they expect.

It would be easy to add length hiding (for all ciphers, STREAM, CBC, AEAD)
to all of TLSv1.x -- simply by defining a compression algorithm that
doesn't compress, but instead adds padding.  Compression algorithms
are allowed to inflate plaintext records up to a size of 2^14+1024 bytes.
And if that (anti-)compression algorithm would add random padding
on both ends of the plaintext, this could also frustrate attacks on
CBC padding and RC4 bias...


-Martin