The birth of Radar

I went to an excellent lecture at my institute with a real engineering gentleman - Laurence Tandy. He reminded me of some of the senior engineers at the Beeb. He clearly had a lot of love for his subject and enjoyed talking about the development of radar from before the war until now. His subject is magnetrons which I've had brushes with when on placement at transmitters (when I was at the Beeb) but never really understood how they work. His explanation was excellent and I came away having really learnt something.
Along with his explanation of the various technique he related several incidents concerning the war and his time spent assisting Robert Watson-Watt - the father of radar. He started as an eighteen year-old lab tech in 1938 and worked his way up to Master Specification Officer for Microwave Power Devices at the government-run Telecommunications Research Establishment from where he retired in 1981.

Lorenz Cipher & Collosus

I went to a superb lecture at my institute - The IET - all about the German Lorenz cipher from the war and the Colossus machine built at Bletchley to crack that code. Tony Sale is a very engaging speaker and clearly a very competent engineer. He is the proprietor of the Computing Museum at Bletchley and has (for the last ten years!) been re-building a working Mk2 Colossus.
The Colossus computers were used to help decipher teleprinter messages which had been encrypted using the Lorenz SZ40/42 machine — British codebreakers referred to encrypted German teleprinter traffic as "Fish" and called the SZ40/42 machine and its traffic "Tunny". Colossus compared two data streams, counting each match based on a programmable Boolean function. The encrypted message was read at high speed from a paper tape. The other stream was generated internally, and was an electronic simulation of the Lorenz machine at various trial settings. If the match count for a setting was above a certain threshold, it would be output on an electric typewriter.

I did take copious notes, but Tony's website is excellent and Wikipedia has good articles on both the Lorenz Cipher, which (like the Enigma) is a symmetric stream cipher, and the Colossus computer.

Tony set a challenge a year ago to receive and break a Lorenz transmission and the German engineer who won was using a 1.4 GHz laptop which, running his own code, took less than a minute to find the settings for all 12 wheels. The German codebreaker 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 Moore's Law, you get an equivalent clock of 5.8 MHz for Colossus. That is a remarkable speed for a computer built in 1944."

Whichever way you think about it the codebreakers at Bletchley shortened the war by months or even years and so can be considered the real heroes of WW2.

Enigma lecture at the IET

Last night I went to a superb lecture at my institute on the German Enigma machine and how they went about cracking it's encrypted messages at Bletchley Park. Dr Mark Baldwin - the lecturer - had brought along his working four-rota machine and gave a demo. The quality of construction was excellent with that sixty year old example still working perfectly. Although I had a vague idea of how it worked he explained in great details the mechanical and wiring details. Having recently re-listened to Steve Gibson's excellent encryption series on Security Now! (episodes 30 to 37) I now see that the Enigma was a good example of how to do encryption. The Germans avoided security by obscurity - the allies had many working Enigmas and had figured out the wiring of all the rota sets before the war even started. The power of he system is in the size of the key-space and it was sloppy practises that allowed the allies to crack the system. Repeated use of sweetheart's names etc. as well as non-random sequences of keys allowed the size of the key-space to be radically reduced and in a symmetric stream cypher these are bad ideas!
Dr Mark Baldwin's Enigma site is here.