The Special Fish Report

Albert W. Small (December 1944)

Page 76

Tony Sale's
Codes and Ciphers

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CX/MSS
TOP SECRET Special Fish Report Page 76

So a little piece of celluloid is used to mark down these columns that form

a good starting block, and the celluloid is slid back and forth to different

matches and partial matches, and the process is repeated until the 61-wheel

pattern has been obtained. The 37-wheel pattern then of course "falls out."

Messages in depth

The fundamental fish equations:

P + PSI' + X = Z

may also be expressed by the parametric equations:

(3) K = P + Z

(4) PSI' + X = K

both of which must usually be solved to read entirely any given message.

Newmanry and Testery both apply themselves to their solution.

Solution of (3) may be done by a process called "anagramming

messages in depth;" or by a process called "cribbing."

Solution of (4) is called "key breaking."

Recovery of key by anagramming messages in depth is well understood

by everyone. While the British are unconvinced of the ease of anagramming

two messages in depth in the Sturgeon machine, which Dr. Levine indicates

can be done without too much difficulty, in his paper on band transposition,

(wait till he gets over here!) they do it all the time on Tunny. Such a

worksheet follows. Procedure is to write out:

Message 1 - - - - - - - -
Message 2 - - - - - - - -
Difference - - - - - - -
N 9
If the difference is a 3, it probably came from 9 (or of course N) and if
8 E
a 5, from 9, and if an F, from N. In any case, they search through the

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