Computer Security and Cryptography

1.7 CRYPTOGRAPHY AND COMPUTERS

There has been a symbiotic relationship between cryptography and the development of high-performance computing systems. As cryptographic systems increased in their sophistication, the need to develop more efficient methods to cryptanalyze them became the stimulus for the development of computers.

Chapter 6 describes two of the three cryptographic systems used by Germany during World War II.

1. Military communications by radio were enciphered by the Enigma rotor system.
2. The Geheimfernschreiber² or T52e manufactured by Siemens and Halske was a binary device in which plaintext was first converted into the 5-bit Baudot code.
3. The Lorenz Schlusselzusatz³ or SZ40/SZ42 also performed encipherment on plaintext converted into binary data.

The T52e and SZ40 devices were on-line devices connected to a teletypewriter. They were both used to protect high-level communications.

The Polish Cipher Bureau started to develop methods to analyze Enigma-enciphered traffic in 1932. The task was given to three recent university graduates – Marian Rejewski, Jerzy Różycki, and Henryk Zygalski, who developed the bombe,⁴ a mechanical computer. When Poland was invaded by Germany, the Polish cipher bureau fled to southern France and then England. Their contributions were great, and although they shared their analysis with the British, they were not permitted to work on the Ultra project – the name of the Allied effort in cryptanalysis.

An excellent narrative of the breaking of the ...