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three more changes to HMAC-MD5-96 & HMAC-SHA1-96 spec
After receiving comments from Bart Preneel and Hugo Krawczyk
and having an e-mail discussion with Hugo over the weekend,
the following changes have been made.
1). Change "no known cryptographic attacks" to no practical
cryptographic attacks.
2). Move paragraph 6 in section 3 to paragraph 2 of section 5
which is a followup discussion on the "no practical" part
from above.
3). Replace the last paragraph in section 3 with (taken almost
directly from [RFC-2104]):
[RFC-2104] makes the following recommendation with regard to
rekeying. Current attacks do not indicate a specific recommended
frequency for key changes as these attacks are practically infeasible.
However, periodic key refreshment is a fundamental security practice
that helps against potential weaknesses of the function and keys,
reduces the information avaliable to a cryptanalyst, and limits
the damage of an exposed key.
The new drafts should be online in the next couple days.
Rob G.
rob.glenn@nist.gov