TheCodeBreakers
both blocks—the same system, interestingly, as the German Army used
at the start of World War I. (This system also backed up the Enigma.)
Each division produced at least three keys for its subordinate units. The
troops heartily disliked the double transposition, however, and cleartext
messages showed a noticeable upsurge. For intelligence and combat
reports, these units used small three-letter or three-digit codes, which
were likewise published by their divisions. Many cipherers preferred their
simplicity to the complexity of the double transposition, and often used
them for orders and other unauthorized messages. A signal officer
complained bitterly of this practice: "Tarntafeln sind kein
Schlusselersatz!" ("Code tables are not cipher substitutes!"), he wrote in a
report. Later in the war, a bigrapic substitution replaced the double
transposition as a front-line cryptosystem, and in 1944 a modification of
the grille replaced that
annaabi.ee 
