Saturday, October 27, 2012

Decrypted Intercepts from the Second World War

GC&CS in Bletchley Park
The National Archives (UK) has published a large file with fascinating intelligence from more than 500 intercepted and decrypted German, Italian and Japanese radio communications between 1941 to 1945. This is a unique release of historical significant information.

The messages, translated into English, originate from the duty officer of Hut 3 (translation, analysis and dispatch) in Bletchley Park, home of the Government Code and Cypher School (GC&CS) and the center of British codebreaking efforts during the Second World War.

The large scale interception, decoding and analysis of millions of encrypted radio and teletype messages was one of the best kept secrets of the war. All these intelligence reports were classified "MOST SECRET" or TOP SECRET ULTRA" and the information was used with extreme caution to protect its source.

The published documents contain a wide range of tactical and logistical information, situation reports, downed aircraft and casualties, interrogation of prisoners, details of meetings of the highest ranking military, situation in occupied countries, the failed assassination attempt on Hitler, theft of art, and much more.

Some decrypts even show grave violations of the Geneva conventions such as direct orders to execute prisoners of war. I'm sure that some of these decrypts helped to convict many high ranked officers during the Nuremberg trials after the war. An historical treasure of information and a must read!

You can download file DEFE 3/573 (select "Download Full Record") from the National Archives or alternatively from my dropbox (right-click link and select Save As...). Note that this is a large 166 MB pdf file that can take a while to download! I you want to sift through many other intercepted communications, please visit this link at the National Archives or use its search engine. More about the breaking of German Enigma machine traffic is found on my website.


Christos T. said...

'Some decrypts even show grave violations of the Geneva conventions such as direct orders to execute prisoners of war'

To play the devil’s advocate, some messages refer to the execution of German POW’s

Dirk Rijmenants said...

Hi Chris,

Indeed, and one German message refer to the Allies keeping German POW's on chains, and in another message they write that the Allies shoot every civilian that leave their village. One can ask how much propaganda vs thruth is in such messages.

However, there's an important detail/difference between the two parties:

1. The Germans wrote execution orders themselves in their messages (that's black on white)
2. The Germans claimed atrocities by the Allies, and in the same time they tell the receiver to make sure that everyone hears about this (this smells like pure propaganda to scare people to continue to fight)

It happens all the time in every conflict. These archives do not show Allied messages that order executions. Having said that, we don't have to pretend that all Allied troops were sweathearts. In the end, they did nuke two cities, but, as they said, only to prevent much more casualties. Whatever has happened, war is a mess.

Christos T. said...

'Whatever has happened, war is a mess'


Pea C said...

Hi Dirk, are there some news about deciphering of the WWII message found recently in GB?

Dirk Rijmenants said...

Hi Pea,

I suppose you refer to the postal pideon's message? There are several problems that make it unlikely that the message will be deciphered. First of all, since a pigeon (open tranfert) was used (between HQ and commander inside the UK, the encryption algorithm is most likely a complex one. Secondly, although its source and type of encryption might be found in the archives, it's key will not be found in those archives, as keys never were archived (security breach). Thirdly, to mount a succesfull cryptanalytic attac, you need lots of statistical data (read many messages). In this case, there's only a very short message. If the algorithm used is complex and/or when codebooks were used (no longer available), the chance of getting it deciphered are virtually zero.

Dirk Rijmenants said...

Regarding the post pigeon, GCHQ confirmed that they are unable to crack the message because it was probably encuphered with one-time pad and they have insufficient information about the message. It seems that my predictions were correct. It isn't because the encryption is 70 years old and we now have supercomputers that we can decipher everything.