Re: How many algorithms per SA/Transform?

["Angelos D. Keromytis" <angelos@aurora.cis.upenn.edu>]

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In message <199703032206.OAA29233@kebe.eng.sun.com>, Dan McDonald writes:
>
>It's a question that I personally think the answer to is, "no".  I can't
>think of any good case (save perhaps protecting headers with one algorithm,
>and the data with another...) where you'd need more than one algorithm of
>each type in a single association.
>

One could also have a mixed algorithm; instead of 3-DES, use DES for
first round, blowfish for second, etc...i can see this used for 2
reasons:
a) DES/Blowfish would be faster than 3-DES, more secure than 2-DES,
and prevent the DES keysearch problem (Blowfish/DES wouldn't
prevent that however - assuming the same key was used for both algorithms).
b) Use a stream cipher and then DES (or the other way around) to
obscure known-plaintext analysis.
- -Angelos



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References:

• How many algorithms per SA/Transform?
• From: Dan.McDonald@Eng.sun.com (Dan McDonald)

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