1. Introduction -- 2. From Julius Caesar to simple substitution -- 3. Polyalphabetic systems -- 4. Jigsaw ciphers -- 5. Two-letter ciphers -- 6. Codes -- 7. Ciphers for spies -- 8. Producing random numbers and letters -- 9. The Enigma cipher machine -- 10. The Hagelin cipher machine -- 11. Beyond the Enigma -- 12. Public key cryptography -- 13. Encipherment and the internet.
