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RE: Reasons for AH & ESP
>>>>> "mouss" == mouss <ipntrq@free.fr> writes:
>> [snip] Well, if you look at IPv4 only, it doesn't make sense,
>> agreed. AH's main feature is that is protects parts of the IP
>> header. But in IPv4, there isn't anything interesting to protect.
>> [snip]
mouss> you are surpising me. Are yo trying to say that a host who
mouss> signs his IPv4 header (thus his source address) using key that
mouss> he negociated with mine, and that based on some external key
mouss> negociation, which is not defined by AH but elsewhere, is the
mouss> same as any spoofing host?
I don't really understand what you're saying. In any case, ESP
provides authentication just as AH does. There are slight
differences, but all important data is protected in both cases.
mouss> I agree that AH relies on the security provided by the key
mouss> negociation protocol. but then it's still good tohave AH while
mouss> "controlling" and improving key ngociation. Fr example, AH is
mouss> good if my negociatio daemon only accepts to talk to daemons
mouss> having a certificate provided by some give authority. The why
mouss> not use ESP here? ebecause I simply don't wanna pay the perf
mouss> overhead when I don't need it.
What performance overhead? The header/trailer overhead is the same in
both cases, and ESP in authentication-only mode has less CPU overhead
than AH because it is significantly simpler.
mouss> Moreover, from a design viewpoint, separating authentication
mouss> and confidentiality is a self-justified purpose.
Perhaps. But not at the cost of a lot of complexity. If AH were as
simple as ESP authentication mode, I would agree with you, but it
isn't -- not by a large margin.
paul
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