Cryptology (from the Greek kryptos 'hidden' and logos 'word') is the science of secure communications. Cryptology is split into two subdivisions: cryptography and cryptoanalysis. The cryptographer seeks to find methods to ensure the secrecy, integrity, and/or authenticity of messages. The cryptoanalyst seeks to undo the former's work by breaking the cryptographer's cyphertext/cryptogram (encrypted plaintext) or by forging coded signals that will be accepted as authentic by the receiver.

Links to the problem sets on this page will be available gradually corresponding to the course schedule.

Cryptography : From World War II machines to unbreakable codes

Part 1. The Hagelin Cryptograph - One of the most popular cryptographs in the 1940's and 1950's. Binary Numbers. Binary Addition. Parity Addition. HBO - Transmission of encrypted password.

Part 2. Modular arithmetic. Modular multiplication. Fermat's little theorem. Public key cryptography. The RSA algorithm.
PDF Addendum to Part Two with Updates on RSA Challenge and Largest Known Prime (as of Feb. 1, 2009)