Captain Walter Fried's Fish Notes March 1944 to January 1945

Page 1

Tony Sale's
Codes and Ciphers

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MOST SECRET CX/MSS

SUBJECT: Fish Notes
TO : CO, SSA, War Dept. Report #F 5
18 March, 1944
1. One of our men, Sgt. Vergine, has commenced work in the
Fish section and is receiving a course of training. I am planning
to participate in this course to some extent and to report on what I
think significant. These reports may duplicate earlier ones and
in many cases, include information and procedures well known at A. H.
However, they my be usefull as a basis for a course of training, as
a means of standerdizing terminology and conventions, and as an orderly
presentation of solution technques. This traffic is deemed of the
utmost importance and I feel sure the British will welcome any assist-
ance we can offer.

2. Trainees, after receiving instruction in the machine and
its operation, are required to memorize the Baudot code. The people
working on hand methods of solution find it necessary to memorize all
combinations of pairs of letters, that is, the full 32 x 32 square.
Others are provided with copies of the square and are also taught the
following simple technique: - place the fingers of one hand on a table
fingers touching the surface representing dots and those raised repre-
senting crosses - then switch each finger corresponding to a cross in
the letter to be combined. The result is read tram the new finger
positions.

3 Nomenclature, Symbols and Conventions
The British use the words dot and cross instead of our dit and x.
Their elementary symbols are as follows:

P = Plain text
Z = Cipher text
K = Total key
X = Chi
(Symbol Psi) = Psi

All of these are used with subscripts to denote a particular impulse.
The subscript i denotes a single inpulse without specification and
similarly ij designates some pair.

Extended Psi is symbolized by and and they call it Psi dash,
not Psi Prime.
The motor wheels are called Mu37 and Mu6l and their combination
is called MB. The actual or total motor results from MB and any
limitations which may be present and is called MT.

In writing out patterns the current convention is to say that
the Psi impulse looks at the motor symbol immediately above it to see
what to do next. In other words, each motor symbol represents what
happens between the encipherment of the impulse directly below it
and the next one to the right. Differenced pattern (which they
designate by Delta as we do) are written under the first of the two dif-
ferenced elements. Then, when the motor pattern is written above the

ARMY MOST SECRET

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