TheCodeBreakers
Referat V 9, which was probably Russia.
Head of Analytical Cryptanalysis (Gruppe TV) was Dr. Erich
Hiittenhain, who also directed that group's instructional activity (Referat
IVd). Referat IVa, which tested German cryptosystems, frequently with
mathematical tools to calculate theoretical limits of security and to find
improvements, was headed by mathematician Dr. Karl Stein, who held
the rank of lieutenant, surprisingly low for so lofty a position. Referat
IVb, headed by Engineer Wilhelm Rotscheidt, used tabulating machines
and special-purpose devices. It invented the prototype of the translucent-
sheet-and-light device used by Pers z to strip additives from a known
code. The unit first worked out the device for two-digit codes and then
extended it to four. Instead of punching out holes corresponding to the
most frequent groups, however, Referat IVb marked them with small
crosshatched disks, and looked, not for the brightest spot, but for the
darkest
annaabi.ee 
