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Re: I-D ACTION:draft-ietf-ipsec-ciph-sha-256-00.txt
In message <Pine.GHP.4.33.0112122244540.6259-100000@domein.esat.kuleuven.ac.be>
, Bart Preneel writes:
>
>For choosing MAC parameters, one has to take into account the
>lifetime during which the system will be used (rather than the
>lifetime of a single key). I believe that 80-bit MACs are
>sufficient for 20 years or more. A MAC of 96 bits may be chosen
>for the alignment reasons mentioned above. A MAC of 128 bits is
>fine but probably too conservative; anything larger is certainly
>overkill and may even harm security in the long run.
What do you mean by "sufficient for 20 years or more"? That that's how long
you expect that it will be safe to use such MACs for new connections?
Obviously, a MAC only has to resist attack while it's still accepted,
unlike a confidentiality key.
--Steve Bellovin, http://www.research.att.com/~smb
Full text of "Firewalls" book now at http://www.wilyhacker.com
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