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*To*: [email protected] (Stephen Benjamin), [email protected]*Subject*: Re: 2 questions: Prime Numbers and DES*From*: Bill Stewart <[email protected]>*Date*: Mon, 19 Oct 1998 17:46:36 -0700*In-Reply-To*: <[email protected]>*Sender*: [email protected]

Go look around for the crypto archives. Some good places have been www.replay.com (or replay.nl?), ftp.funet.fi, ftp.ox.ac.uk, ftp.dsi.unimi.it. Look for the Cyphernomicon and the sci.crypt faqs. Altavista is your friend. If you want code for DOS, remember that you can compile and run C programs on DOS, and a bare-bones DES program that uses stdin and stdout should do just fine. For prime numbers, read some books! Bruce Schneier's book is a good place to start. Also, look around on www.rsa.com. The standard approach to generating large prime numbers is to generate large random odd numbers of the length you want and see if they're prime. Actually proving primality is hard, but there are tests for "probable primes" that appear to be independent - so you take the candidate numbers and run 20 iterations of a test to get probability 2**-20 or 2**-40 of error. Depending on speed of things, it's usually more efficient to run a sieve to eliminate multiples of small primes (certainly 2,3,5,7, possibly many more) since those tests are often faster than the probable primality testing. If you want to _understand_ this stuff, as opposed to merely using it, you'll need some math, specifically number theory dealing with primes and modular arithmetic. But start with Schneier. At 03:13 PM 10/18/98 -0400, Stephen Benjamin wrote: >1. How can I generate 2 large prime numbers? I doubt I could create 2, >100-digit prime numbers in my head :-) > >2. Is there an implentation of DES in perl? I didn't see a link to one >on the export-a-sig page. If not perl, is there one for DOS? I'm >looking for a bare bones one, not something with tons of features >and a GUI. A perl or dos version of the unix "des" program would be >preferable. Thanks! Bill Bill Stewart, [email protected] PGP Fingerprint D454 E202 CBC8 40BF 3C85 B884 0ABE 4639

**References**:**2 questions: Prime Numbers and DES***From:*[email protected] (Stephen Benjamin)

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