If you or anyone else knows of publications that deal with/expand upon what I have written here, I would like to know.
An analysis of the breaking and reading of German traffic by the British, (Ultra) , that was reading Russian traffic, strongly suggests that the Russians were seemingly* unaware that their codes were being read. This was ONE of the reasons why the British were VERY careful as to what information they passed to the Russians. They knew that the Germans were reading the Russian traffic.
* I read somewhere many years ago that the traitor Philby passed onto the Russians a number of directly transcribed Ultra decrypts of German Enigma messages. So who knows?
Probably the greatest tactical use made by the Germans of reading British traffic, was in the North Atlantic by the reading of Naval Cypher No 3.
There has been some writing as to the tactical use for specific convoys by the Germans from the period October 1941 up to mid June 1943, when the cypher was dropped. There are also fleeting references to the use of fake/decoy/ghost radio traffic by British escort groups, but nothing as to the tactical effectiveness of such procedures.
I am NOT aware of anything of substance beyond this on both sides that has been released to date. This maybe because of the extreme sensitivity of the subject, ie radio counter intelligence. eg the use of false data regarding U boat positions inserted in Naval Cypher No 5, I only found buried in ONE of the above top secret Ultra histories, and that was written by an American. No other mention anywhere so far, but ... I may be out of date by now.
The reading by the Germans of the British Fleet code in the spring of 1940 led directly to the interception of the Glorious. Bletchely Park warned Admiralty of the northward movement of German heavy units through traffic analysis, but this was ignored.
The first break into German Enigma (German Air) was made at about this time by the first Turing machine, which had just gone on line.
Fascinating information. Thank you for posting it. It would be very interesting someday to know the extent of Russian breaking of German codes and the reverse. Also interesting would be an analysis of the tactical use the Germans made of these breaks in allied codes.
Typex. first used for naval traffic in 1939.
Similar to the German Enigma machine. The Germans captured a British Typex machine in France in 1940, but as it lacked the set of drums, the Germans decided that it was not possible to break into the system and so no further work was done on the problem.
Typex was used for the first two years of the war for messages between shore stations, but from then on there was the gradual deployment to ships afloat.
From November 1943 there was the use of combined US/UK cypher machines for naval traffic, and from April 1944 for the combined US/UK services. The Germans made efforts to break into this system without success.
UK Fleet Code
This was a low grade system.
It gave some movements of UK convoys and reports on German U boats in Home Waters.
The Germans partially broke into this code, which was usually changed about once a month. It took about two weeks for the Germans to break into a new edition.
Combined US/UK Assault Code. (A low grade system)
In use for Operation Neptune until the 20th of June 1944. The Germans broke into this to an extent, enabling them to read partially the details of the movements of UK convoys to the Normandy beaches.
Loxo (Small Ships Code)
A low security system.
Introduced for Home coastal waters in August 1941. This code was changed daily, but the Germans routinely broke the code between two to nine hours each day.
Used for coastal escorts, MTBs and minecraft, it helped the Germans with their E boat operations.
Various editions were published, but failed to defeat the Germans decoding efforts.
Introduced in September 1943.
Used mainly for movements of landing craft and associated small craft.
By early 1944 the Germans were reading up to 95% of this traffic. The reading of Cofox gave the enemy in the spring of 1944 the dispositions of most of the landing craft on the east coast of the UK. Cofox also gave data in a general manner, of minesweeping and MTB operations in the English Channel and along the East coast of the UK.
Air Sighting Reports Code.
These code were changed daily and easily read by the Germans and the Italians.
The Germans needed about 40 to 45 intercepted messages to break the daily change, and with a high volume of messages, this was usually done within a few hours. In addition to sighting reports, messages for sighting reports, messages that also gave weather and exercises reports were also of value.
A low grade system.
Naval air sighting reports changed daily.
Not so easily broken as Skyo (RAF), because of th much lower number of daily messages transmitted, (10 per day on average).
In July 1942, new higher grade editions of Skyo and Nyko came into use which greatly reduced the enemy's successes.
One Time Code Pads.
Initially introduced for use between shore stations and then from June 1941 to Cin Cs afloat. Used for the most sensitive messages at Ultra level and ABOVE. Introduced in June 1941 for Cin Cs afloat after the British were able to read CURRENTLY* the German Naval Enigma traffic.
The Germans appear to have not placed any effort into breaking this traffic and it remained secure for the rest of the war.
One Time Code Pads for individual Ships.
A very high grade security system for merchants sailing independently, fast tankers and convoy stragglers.
The Germans appear to made no attempt to beak into this system, considering it to be similar to the one time code pads for CinCs afloat.
* Able to read encrypted German Naval messages sent on Enigma within 24 hors of being intercepted.