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Stuart Rutter, a developer at Square Enix in London. Enjoys cryptography, search algorithms, competitive coding, and start-up ventures.


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WW2 Carrier Pigeon Code

November 24th 2012

My dad and I have been reading Leo Marks' Between Silk and Cyanide. We were quite excited to hear a recent news article relating to a WW2 carrier pigeon found in a chimney with a secret message hidden in a capsule on its leg.

Here is the message that was recovered:

The message would have been encoded using one of the many ciphers, or poems used by the Special Operations Executive during WW2 - here are my thoughts on the message and the possibility of decoding it.

  1. I don't think 27 1525/6 relate to a date / time. They are probably parity checks, and/or a pointer to a worked-out-key (WOK). Also, there are 27 groups of 5 characters, so the 27 could be to validate code groups.

    It was written on the message that there were two copies of this message sent, so it is possible that 1525/6 relate to the keys used to encode them. The usual practice for this was that the agent in the field carried with them worked-out-keys written on silk, so that they could be easily concealed under clothing and burnt after use, these keys were then used to encode the message, the reference 1525 could relate to the key that was used to encode this message.

    So if this was the case the only hope in decoding the message would be to find out the keys used by this agent. I may have found a good place to start looking for these at the National Archives at Kew, more on this below.

    Another reason why I don't think "1525/6" is a date/time is because in the original message there are spaces for the date which are blank. I think it would be highly unlikely that the person writing this would write the date somewhere other than in the date box!

  2. There are two peoples handwriting on the message. I assume one is the SOE agent and the other the pigeon handler. The pigeon handler wrote the pigeons ID, and "lib 1625" - which could well be the French for "liberté", or the release time of the pigeon (assuming that the message came from France). Either way, I don't think that "lib 1625" has anything to do with decoding the message, because it wasn't written by the agent.

  3. I think the best chance of cracking this would be to spend a few days at the National Archives at Kew. My opinion is that a Playfair cipher was used, and I just hope that we can identify the field agent because otherwise, and without this information, the message could well be indecipherable.

    This would be a interesting place to start at the national archives: Special Operations Executive: Playfair and Wireless Operators Codes Nominal Card Index

    This series contains the nominal Playfair code card index showing code details for each agent or wireless operator in the field. The Playfair code (invented by one of the devisers of the telegraph, Sir Charles Wheatstone) was that used by SOE agents up to 1942, when its weaknesses were demonstrated by Leo Marks and the code was progressively replaced by more secure coding practices.

    For each agent, the index card shows the letter square to be used and the phrase it was derived from, along with the various security measures agents were to apply to their messages sent from the field. The cards include a date of which the meaning is now not clear, but which may be the date of the agent being trained in the use of the code.

    Kew is only 10 mins from where I live so if I get a chance in the week I'll see what I can unearth.

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