From: Jiri Baum <jirib@sweeney.cs.monash.edu.au>
Date: Thu, 3 Aug 95 00:59:27 PDT
To: tcmay@sensemedia.net (Timothy C. May)
Subject: Re: Provably Correct Crypto?
In-Reply-To: <ac43be3d13021004ec3b@[205.199.118.202]>
Message-ID: <199508030758.RAA10894@sweeney.cs.monash.edu.au>
MIME-Version: 1.0
Content-Type: text/plain


Hello Ray Cromwell <rjc@clark.net>, patl@lcs.mit.edu
  and tcmay@sensemedia.net (Timothy C. May)
  and cypherpunks@toad.com

> At 4:15 PM 8/1/95, Ray Cromwell wrote:
...
> >PGP, but in the algorithm itself. RSA-in-4-lines-perl is probably
>                                    ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
> >provably correct.  To guard against trapdoors in PGP, you should
>  ^^^^^^^^^^^^^^^^^
...
[emphasis tcmay]

To which tcmay responded:

> This doesn't seem likely. I mean, doesn't "RSA-in-4-lines-of-Perl" *of
> necessity* make use of external library/utility functions? Such as the "dc"
> math routines for the PRNG? Part of its compactness is that it makes use of
> available libraries.
...

AFAIK (my 4 lines might differ from yours), there is no PRNG in the
4 lines of perl. The key is supplied as a parameter, and no guidance
to its generation is given in the implementation.

You are right about the dc, but it only uses that for modular exponentiation,
which is a lot easier to prove correct than PRNG.
Which is not to say that it *has* been proven.


I guess that makes me a nit-picker...

Jiri
--
If you want an answer, please mail to <jirib@cs.monash.edu.au>.
On sweeney, I may delete without reading!
PGP 463A14D5 (but it's at home so it'll take a day or two)