Whilst we were visiting Cambridge last month, we had an opportunity to take a trip to Bletchley Park. During the second world war the estate became the Government Code & Cypher School, where many of the brightest mathematicians and engineers of the time laid out the future of modern computing. Today the original buildings have been taken into a trust by volunteers and the large campus houses a number of museums, open to the public.

I have always wanted to visit but even more so since I found this passage in my Grandfather’s military record, from the Military Archive in Cathal Brugha barracks.

Syko Code Report

The entry is very cryptic; what is it referring to? He worked in G2, the Irish military intelligence organisation during the war (or ‘emergency’ as we like to call it). When I searched for the mysterious ‘Syko Code’ mentioned in the report, I was directed to the Park museum where they have one of the machines on display.

Bletchley Park is not pretty, it is a rather stuffy victorian house surrounded by dilapidated one-storey buildings of both brick and wood, painted white. The complex has a curiously anonymous understated air and does not look at all as if 9,000 people worked there.

The trust at Bletchley Park have restored the huts and equipment contained the Turing Bombes and Tommy Flower’s Colossus, but they have done so on a very small budget which has ensured that the complex is not over-restored and retains its original feel. Most of the important work was done in hastily-erected huts which were not intended to be permanent structures, you can see one being restored here.

Hut at Bletchley

We went on a tour with one of the volunteer guides which took us through from the construction of the first bombe to the electric relay machines that were necessary to decode the more complex ciphers that were in use towards the end of the war.

The staff made a really good job of illustrating the chronological progression of the code-breaking equipment as the cipher complexity ramped up. It is also possible to see how it ties in with Turing’s pre-war papers which are all presented in the museum.

Turing Bombe

Seeing the machines* in situ* conveys a very good sense of how cramped and gloomy the working conditions were. Once the Colossus machine starts running it also becomes very hot and noisy.

The guide painted a vivid depiction of the hut, blast walls over the windows, filled with cigarette smoke, hot in summer with the machine on and cold in winter when they pushed messages through a pipe connecting the decryption and decipherment huts.

Operating a bombe meant a full 8 hour shift on your feet and the Wrens only had a partial picture of the process. Communication between huts was forbidden and one Wren only discovered that the phone she used to deliver results connected to a neighbouring hut when she came back to visit the interpretive centre recently.

It seems the Bombe was a universal enigma machine. The intention was to ‘remove hay from a stack to find the needle’ i.e. brute force the messages, and each 3 wheels on the bombe replicates one enigma machine. As you can see from the photographs, each bombe can attempt many parallel attacks.

Eventually this wasn’t enough. Although the Bletchley Park codebreakers made many optimisations and shortcuts, the Germans could exponentially increase the key size by adding wheels to their Enigma machines.

The Lorenz machines used towards the end of the war were invulnerable to Bombe decryption but, with D-Day as a deadline, Tommy Flowers managed to deliver the first valve-driven electronic relay computer, Colossus.

Reconstruction of Colossus

Colossus was the real reason that the facility was shut down and dismantled after the war. Churchill wanted to make sure the Russians knew nothing of the decryption successes and there was a spy, John Cairncross, working in the facility.

The site also houses the National Museum of Computing, featuring an amazing array of familiar old machines. But the part I was really waiting for came at the end of the day when we visited the exhibition centre. Right at the back, behind the much more impressive Enigma and Lorenz machines, I found the Syko display case.

The Syko Display

There are two machines, each with a description. They have carry cases and metal trays for holding messages. Evidently they were intended to be portable and they required no power source. Even from looking at the layout of the machine, it is obvious that the cipher is not very complex and in fact the German B-Dienst service cracked it during the war.

This does not particularly detract from the usefulness of the cipher; with regular changes of key, it could be used safely for air and sea traffic. 80 percent of the intercepted radio messages were read. However, only 10 percent of them were decrypted in time to take effective action

Syko – Mark I

“A low-grade British mechanical cipher machine used for ground to air instructions by the RAF in World War Two. This cipher machine is very fiddly to use as the paper strips tear very easily.

This wooden-cased version dates from 1936 and is a prototype.”

Syko – Mark II

“This cipher machine is an improved version of the Syko Mark I British mechanical cipher machine used for ground to air instructions by the RAF during World War Two.

The Mark II Syko utilised sliding letters instead of paper strip and was more durable. The Mark II was used in the later stages of World War Two.”

I was delighted to finally get to look at the machine after chasing up the references but it did occur to me that it was unusual for the RAF to share encryption resources with the Irish intelligence service during the war when we were a neutral country. There was definitely a link between British and Irish intelligence at this time and some of the information collected in Ireland would have been of great interest to the RAF.

It appears that my Grandfather was also involved in collecting intelligence at Foynes airport and tracing bomber flight paths. The service was also involved in picking up and debriefing downed pilots from both sides. Maurice Walsh’s book on G2 describes the involvement of the head of signals at G2 (Richard Hayes) in the code-cracking effort; it details the contributions of G2 in breaking the Goertz cipher and a visit from ‘the head of their Cipher Department at Bletchley’.

Perhaps we were given the Syko machines in recognition of this collaboration or perhaps just so that British intelligence could monitor anything sent using the machines. There is a precedent for this; many former colonies were given Enigma machines by the British in the post-war period without being told that MI6 could read their messages. We also spent 1 million on a Crypto AG machines during the Anglo-Irish negotiations in the 1980s that later turned out to have a back-door for MI6.