I’ve written about the compromise of the French War Ministry’s FLD code by the codebreakers of the German High Command's deciphering department – OKW/Chi, however up to this point I hadn’t been able to find the official designation of this cryptosystem.
Recently I’ve discovered some clues that might clear things up.
According to the available sources this cryptosystem was used for ‘the cypher traffic between the French War Ministry and the army groups, armies and home authorities’.
The new finding aid to the TICOM collection of the German Foreign Ministry’s Political Archive has certain entries that read:
NR 3684 – ‘F4ZCUW 110’ German notes on the above French Defense Area cipher
NR 3615 – F4ZCUT’ German notes, 1931, on French code as above, used by the Defense Areas HQ’s from Schliersee.
The finding aid also mentions the French code F-90 which might have been the predecessor to F-110.
The French code F-110 is mentioned in one of Erich Huettenhain’s reports:
What was the French designation for the system that the Germans called F-110?
Possibly Code R.A.
The finding aid says:
NR 1736 – Code RA, French military code sheets and instructions for use. Various dates 1933-39 March and July 1940-42 from Schliersee.
Why do I think that Code RA was used by the French War Ministry and the Army Groups?
In the book ‘KODY WOJNY. Niemiecki wywiad elektroniczny w latach 1907–1945’, p1.046 there is a copy of a French report dated 16 April 1940.
Un code R.A. avec additif et son procede de surchiffrement (clef ZERO S.2.) pour permettre de correspondre a l'Intérieur de la Métropole avec les Autorités et Etats-Majors dotés de ce document (notamment commandants d' armes).
R.A. a code with additive and process for its super-encryption (key ZERO S.2.) To allow a match the interior of the metropolis with the authorities and with staffs of this document (including commanders of weapons).
I hope my friends in France will look into this case. I can’t solve everything by myself!