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Re: Photuris questions
> From: Hilarie Orman <ho@cs.arizona.edu>
> The error message I'd like to recommend is for the case where one side says
> to the other "I really wanted you to establish an ESP SA for sending
> stuff to me; you chose not to, I'm displeased."
>
You seem confused. Since _I_ establish the ESP SA for sending stuff to
_me_, this would be a pointless error message. Remember, SPIs are
Destination oriented.
I did add a message for when I want to _send_ ESP, and _you_ didn't
establish an ESP SA. That's the correct direction. That's how I had
interpreted your suggestion, which is a very good idea.
> If both AH and ESP are indicated by one SPI, then how are the keys for
> the two modes assigned? Are there two separate keys?
>
The same key bitstuff is reused. There are two separate session-keys
only when two separate SPIs. SPI => session-key, remember?
Note that specifically using MD5 and DES, there will be two slightly
different keys anyway, since MD5 uses the entire generated key, while
DES uses only the first 64-bits and inserts parity. But they are
obviously algorithmically derived.
I added more explicit keying instructions long ago. The new draft
should be coming to a directory near you Real Soon Now, after Phil and I
go over the new text today. But, since you have been so helpful in the
past, I'll quickly send you a private copy for review. Particularly as
I have some questions on the text and references that you sent previously.
> If the number of bits required for supporting all the underlying algorithms
> exceeds the number that Photuris can safely deliver, is there an error
> message to that effect? If all the algorithms must have independent keys,
> this situation can occur under realistic scenarios.
>
Huh? Safely deliver? Sounds like you are getting theoretical on me
again. I certainly don't have an algorithm for "safeness" of bits!
The implementation just has to be smart enough that when MD5 delivers
128-bits, it can't pick an algorithm that requires a key of more than
128-bits. DES will always be implemented, so no problem there (56-bits).
Bill.Simpson@um.cc.umich.edu
Key fingerprint = 2E 07 23 03 C5 62 70 D3 59 B1 4F 5E 1D C2 C1 A2
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