Bits, binary numbers, the XOR cipher, perfect security and one-time pads. For MAT 140: Introduction to the Mathematical Sciences, at Franklin College.

1. Cryptology
Day 3: First look at
computer ciphers
MAT 140: Introduction to the
Mathematical Sciences
19 September 2008
Robert Talbert, PhD
Associate Professor of Mathematics
and Computing Science
rtalbert@franklincollege.edu

2. Recap of Day 2
• Integer congruence modulo n
• Using integer congruence to make and break shift ciphers
• Idea: Representing text characters as numbers and then
using math to manipulate them

3. Unicode
Worldwide standard for
representing characters from the
keyboard and various languages
in numerical form