A Prime Patent; July 1995; Scientific American Magazine; by Garfinkel; 1 Page(s)

Roger Schlafly has just succeeded in doing something no other mathematician has ever done: he has patented a number. The seemingly bizarre event is the latest twist in the saga of assigning software patents that has vexed the U.S. Patent and Trademark Office for more than 20 years. "I'm sure if you just went to someone and said, 'Can you patent a prime number?' they would say to you, 'No, that's ridiculous, ' " says Schlafly, a computer consultant who lives near Santa Cruz, Calif.

Schlafly, of course, hasn't patented just any number. His figure--which is nearly 150 digits long--has a property that makes it possible to take a certain shortcut when performing modular division. A little improvement in division is big news for people using the Diffie- Hellman public-key cryptography system, which uses repeated modular divisions as a tool for encrypting and decrypting secret codes. Cryptographic keys are typically numbers hundreds of digits long, so a small improvement can mean a big savings in time.