Once the simple substitution cipher and the Vigenère cipher had been cracked, the search was on even better ciphers. As the 20th century progressed, encryption moved from pencil and paper to the electro-mechanical Enigma, then to computer algorithms, and then to public key cryptography. And at the end of the century quantum cryptography has become a reality.

However, the Black Chamber ends here. To find out more about 20th century cryptographyor cryptography in general, then you could:

- visit Crypto Corner at simonsingh.net
- visit the Crypto Links at simonsingh.net
- obtain The Code Book by Simon Singh
- obtain the interactive CD-ROM on cryptography.

In particular, I would recommend the CD-ROM, which is an interactive version of The Code Book. It includes:

- Encryption tools,
- Codebreaking tools,
- Video clips,
- Code messages to crack,
- Material for teachers,
- A realistic, virtual Enigma cipher machine,
- A beginner's cryptography tutorial,
- A history of codes from 1,000 BC to 2000 AD,
- Material for junior codebreakers,
- Interviews with Whit Diffie and Clifford Cocks.

From left to right: Figure 1: Three rotors ready to be placed into an Enigma machine. Figure 2: The internal workings of an American M207 encryption machine. Figure 3: German CD-57 handheld encryption device.