Re: [9fans] one weird trick to break p9sk1 ?

[Richard Miller <9fans@hamnavoe.com>]

23hiro@gmail.com:
> sorry for ignoring your ideas about a p9sk3, but is your mentioning of
> ocam's razor implying that dp9ik is too complicated?
> is there any other reason to stick with DES instead of AES in
> particular? i'm not a cryptographer by any means, but just curious.

My comments are about p9sk1; I'm not implying anything about other
algorithms.  When working with other people's software, whether
professionally or for my own purposes, I try to take a
minimum-intervention approach: because it's respectful, because of
Occam's Razor, because of Tony Hoare's observation that software can
be either so simple that it obviously has no bugs, or so complicated
that it has no obvious bugs.

I thought of 3DES in the first instance because of this desire to be
minimally disruptive.  Support for DES is already there and tested.
3DES only needs extra keys in /mnt/keys, and because 3DES encryption
with all three keys the same becomes single DES, there's a graceful
fallback when users have access only via an older client with
unmodified p9sk1. Obviously the server ticket would always be protected
by 3DES.

This is only the first scratching of an idea, not implemented yet.

I've got nothing against AES. I'm not a cryptographer either, but I did once
have to build a javacard implementation for a proprietary smartcard which
involved a lot of crypto infrastructure, and had to pass EMV certification.
Naturally that needed AES, elliptic curves, and plenty of other esoterica
to fit in with the existing environment and specifications.


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