## TITLE: Is 3828001 prime? Primality testing: a key ingredient for encryption |

**Kathryn Lesh**

Union College

November 7, 2011

5 pm

Bailey Hall 207

Refreshments will be served in Bailey Hall 204 at 4:45

Have you ever bought something online using a credit card on a secure website? If so, you were a user of public-key encryption, and most methods of public-key encryption have a prime number lurking somewhere in the background (or even right up front!). For small numbers, like 17, it’s practical to check primality by trial division. (Is 17 divisible by 2? By 3? By 5, 7, 11, or 13? No? Then 17 is prime.) But for numbers of the size needed for encryption methods, trial division is impractical, because finishing the job would take longer than we expect the universe to survive. In this talk, we’ll explore some ways to find large prime numbers for use in cryptography by sneakier methods than trial division.

For additional information, send e-mail to math@union.edu or call (518) 388-6246.

Union College Math Department Home PageComments to: math@union.edu Created automatically on: Fri Jan 19 16:42:35 EST 2018 |