M4 Steckers

Tony Sale wrote:

> All, In thinking about the M4 "find the Steckers" problem I decided to
> do what BP would have done, look for human errors in the preparation
> of setting sheets, and I found them.
> In a 1944 months setting sheet, the person preparing it had obviously
> got tired of doing them. On any one day there are sequences, sometimes
> four long of incremented letters such as, AL BM CN DO.
> I suggest that in working through letter pairs, at least two and
> possibly three successive letter increments are tried at the same time.

I don't have any more examples, but it is clear that Bletchley Park was 
looking out for this kind of thing throughout the war.

There is a wartime memo in the US National Archives showing that in late 
1944 BP detected examples of Umkehrwalze D pairings from one Luftwaffe key 
having been used to construct the Stecker pairings for another.  This memo 
was written by the same Reg Parker mentioned by Gordon Welchman in "The Hut 
6 Story" as having detected repeated portions of Enigma keys back in 1942.

I'm not aware of any similar examples from German Naval traffic, and in 
general the Luftwaffe was much less conscious of cipher security than its 
marine counterpart.

Tony's example is rather more egregious.  I believe there were instances 
where local Luftwaffe offices made up their own keys rather than receiving 
them from a central cipher office, and in those cases it seems more likely 
that poor practices could be adopted.  Presumably all of these organizations 
were getting pretty short on staff by that stage of the war, while the 
demand for key sheets was increasing as the Luftwaffe (and for that matter 
the German Navy) started to segregate their networks into more and more 
separate keys.

Phil Marks