Re: [Emu] EAP-GPSK: Ciphersuites

Interesting idea, but what does it gain you?  Why not just use an 
AES-CBC and CMAC ciphersuite?

-- 
t. charles clancy, ph.d.  |  tcc@umd.edu  |  www.cs.umd.edu/~clancy

Lakshminath Dondeti wrote:
> I guess we agree to disagree.  The addition integrity checksum is 
> spurious in my view and I believe we can define things so that combined 
> modes can be employed without encrypting anything, so I am somewhat 
> confused here.  What's your opinion on the latter part of my email?
> 
> thanks,
> Lakshminath
> 
> At 05:12 PM 8/22/2006, Hannes Tschofenig wrote:
>> Hi Lakshminath,
>>
>> Lakshminath  Dondeti schrieb:
>>> At the expense of generating some confusion, here is my take on this:
>>> The objection is to having to carry multiple integrity checksums in 
>>> GPSK, if we used the combined mode *and* an integrity algorithm.
>>
>> I don't agree with you. There is no reason to optimize a few bits in a 
>> pre-shared secret method.
>> Note that we are not talking about a protocol for data transfer.
>> We wanted the flexibility to use different cipher suites. We do not 
>> only want to use cipher suites that provide authenticated encryption 
>> (since we almost have nothing to encrypt; currently 1 bit and almost 
>> no EAP method provides this functionality).
>>
>> Ciao
>> Hannes
>>
>>> I think CCM is fine for instance, the only catch is that we need to 
>>> make sure and define AAD for CCM carefully to include appropriate 
>>> data into the integrity checksum calculation.  So, once we define CCM 
>>> as the mode, we shouldn't need AES-CMAC-128 if encryption is being used.
>>> I would suggest using CCM and specifying the use of it fully so it 
>>> can be used without misunderstandings.  If you want me to put some 
>>> time into writing that up, let me know.
>>> cheers,
>>> Lakshminath
>>> At 10:55 PM 8/20/2006, Hannes Tschofenig wrote:
>>>> Hi all,
>>>>
>>>> the current version of the document
>>>> http://tools.ietf.org/wg/emu/draft-clancy-emu-eap-shared-secret-01.txt
>>>> still supports AES-EAX:
>>>>
>>>>    
>>>> +-----------+----+-------------+---------------+--------------------+
>>>>    | CSuite/   | KS | Encryption  | Integrity     | Key 
>>>> Derivation     |
>>>>    | Specifier |    |             |               | 
>>>> Function           |
>>>>    
>>>> +-----------+----+-------------+---------------+--------------------+
>>>>    | 0x000001  | 16 | AES-EAX-128 | AES-CMAC-128  | 
>>>> GKDF-128           |
>>>>    
>>>> +-----------+----+-------------+---------------+--------------------+
>>>>
>>>> At the IETF#66 EMU meeting AES CCM was suggested.
>>>>
>>>> Later, it got the impression that AES-CBC was more appreciated. 
>>>> Should we update the draft with AES-CBC?
>>>>
>>>> Ciao
>>>> Hannes
>>>>
>>>>
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> 
> 
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