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Weak keys
If I understand it correctly, the current IKE spec says that the keys
for each of the transforms are taken from the start of the keying
material, except for DES where you skip bytes until what you find
isn't one of the weak or semi-weak keys listed.
This doesn't seem to be complete, because it doesn't take into account
the weak keys of other cryptosystems (such as 3DES, IDEA, and
Blowfish).
It also doesn't sound like it will interoperate if new weak keys are
discovered and one side is updated to recognize those weak keys (since
the two sides will extract different substrings from the keying
material). After all, the listing of weak keys is subject to growth
as more is learned about the systems in question.
One possible interpretation:
1. the key extraction rules are exactly as specified and stay that way
forever.
2. any other weak keys are handled by rekeying immediately.
Is that the intent? If not, how are weak keys handled?
paul
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