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Date:      Tue, 20 Jun 95 0:28:22 MDT
From:      terry@cs.weber.edu (Terry Lambert)
To:        mark@grondar.za (Mark Murray)
Cc:        wollman@halloran-eldar.lcs.mit.edu, current@freebsd.org
Subject:   Re: Crypto code - an architectural proposal.
Message-ID:  <9506200628.AA24718@cs.weber.edu>
In-Reply-To: <199506200613.IAA01182@grumble.grondar.za> from "Mark Murray" at Jun 20, 95 08:13:34 am

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> > The net effect of this is that CDROM distributions will become *more*
> > difficult to crypto-enable than they currently are.
> 
> Right. I'll stick with what we currently have (more-or-less). Is there any
> reason that libcipher cannot be merged with libdes?

I can't think of any off the top of my head (doesn't mean there aren't
any, however).

> > I agree that the hack-attack prevention is a poor reason for slowing down
> > crypt().
> 
> Thanks! Are there any other (potential) reasons why crypt(3) should be slow?

Yes.  The ANSI standard defining DES states that particular steps will
be followed during the process.

Implementations, such as "fastcrypt", can't claim conformance to the
published standard because they mathematically simplify the process
in order to get a speed up (losing conformance in the process).

It is also possible to build a crypt that is useless for other than
password forward encryption by going through other mathematical
simplifications to the algorithm (like assuming a constant table,
etc.) and precomputing the values for some of the resulting
calculations so that they will not have to be redone each time the
thing is run.

Boils down to (1) mathematical transformation (standards violation) or
(2) robbing the algorithm of generality (another standards violation).


Man, and I'd promised my poor old decrepit mom that I wouldn't go
discussiong crypto any more... ;^).



					Terry Lambert
					terry@cs.weber.edu
---
Any opinions in this posting are my own and not those of my present
or previous employers.



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