Xref: utzoo news.sysadmin:3138 comp.mail.uucp:4848
Path: utzoo!attcan!utgpu!news-server.csri.toronto.edu!clyde.concordia.ca!uunet!cs.utexas.edu!usc!ucsd!pacbell.com!pacbell!sactoh0!cds1!matt
From: matt@cds1.UUCP (Mathew Di Nicola)
Newsgroups: news.sysadmin,comp.mail.uucp
Subject: Re: Passing proprietary messages through competitors or other sites
Keywords: RSA
Message-ID: <6iZZm1w162w@cds1.UUCP>
Date: 28 Jul 90 02:31:28 GMT
References: <12687@netcom.UUCP>
Organization: Carmichael DOS Systems, CA
Lines: 33

ergo@netcom.UUCP (Isaac Rabinovitch) writes:

> I'm out of date on encryption software, but didn't there use to be
> "public key" algorithms?  You make up a private key, pass it through
> a special procedure to produce a public key.  You then publish the
> public key.  Anybody who knows the public key can send you an
> encrypted message, but you need the private key to decrypt the
> message.  Seems tailor-made for this problem.
> -- 
Yeah, the public key cipher that I'm familiar with is called RSA (Rivest
Shamir Adelman) and was developed in 1978 at MIT.  The program generates
three 80-200 digit prime numbers.  The first two can be published to all
the world, and are used to encrypt data only.  The only way to decrypt
it is to use the third (secret) key.  It works quite well, because you
don't have to deal with DES-type single-key encryption/decryption.
There's only one drawback -- encrypting, decrypting, and generating RSA
keys takes a long time.  Math coprocessors and 386s help a lot (everyone
has a 386 with a coprocessor, right? ha ha...), but if security is
desired, that's the way to go.

Incidentally, with a 50-digit key, cryptanalasys takes 3.9 hours.  With
a 100-digit key, cryptanalasys takes 74 years (WITH a computer), and if
you REALLY want security, a 500-digit key takes 4.2 * 10^25 years (the
universe is only 1.5 * 10^10 years (roughly).  If anyone is interested,
I have a Shareware program for MS-DOS that will do RSA, DES and a few
others....  e-mail me, and I'll figure out a way to get it to you.

--Matt
------------------------------------------------------------------------------
Mathew Di Nicola			      Sacramento, CA, USA

UUCP= pacbell!sactoh0!cds1!matt
------------------------------------------------------------------------------