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Re: Generating 3DES keys from SKEYID_e



Paul Koning wrote:
> 
> >>>>> "Glawitsch," == Glawitsch, Gregor <Gregor_Glawitsch@nai.com> writes:
> 
>  Glawitsch,> Stephane, do you realize how large 2^128 is?
> 
> While it doesn't matter for 3DES (since the effective key strength is
> less than 2^128) this issue will matter for AES.
> 
> Yes, 2^128 is a big number.  But if you want to claim support for
> ciphers with long keys, by his argument you need a PRF of
> corresponding size.  There's something to be said for that.
> 
> The alternative, of course, is not to support keys larger than 128
> bits.  That's in practice not a bad idea.
> 
>        paul

Another alternative would be to use Tiger as the hash. That is a
SHOULD in RFC 2409 and gives a 192-bit hash. 
http://www.cs.technion.ac.il/~biham/Reports/Tiger/


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