Breaking Ciphers on a 5.8MHz Pentium?

The UK’s National Codes Centre recently ran a competition for amateur codebreakers to try their hands on breaking one of the original WW2 codes (Lorenz Cipher) using modern PC hardware. The National Codes Centre at Bletchley Park (known as “Station X” during the war) is a museum and heritage site for early computing as well as codebreaking. In a nice irony, the winner of the competition was a German programmer, Joachim Schueth, who ran his software on a 1.4 GHz laptop with NetBSD as the O/S, beating the original Colossus codebreaker by a factor of hours. The original Colossus could break the code in 3 hours and 15 minutes, whereas Schueth’s code took just 46 seconds.

On the performance difference, Schueth himself said: “My laptop digested ciphertext at a speed of 1.2 million characters per second – 240 times faster than Colossus. If you scale the CPU frequency by that factor, you get an equivalent clock of 5.8 MHz for Colossus. That is a remarkable speed for a computer built in 1944. Even 40 years later many computers did not reach that speed. So the Cipher Challenge would have been very much closer had it taken place 20 years ago.” That’s right, not GHz, but MHz. The original Colossus was not so much a Pentium, but rather a Z80.

At Bletchley Park, they have a working Colossus which was lovingly rebuilt over many years by a team of enthusiasts, with help from some of the original designers. The Colossus MKII can be seen working by visitors to Bletchley Park.