The Special Fish Report
Albert W. Small (December 1944)
Page 94
Tony Sale's
Codes and Ciphers
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CX/MSS
TOP SECRET Special Fish Report Page 94
Getting a start in Turingery when 300 letters or more of key are
available (and motor dottage is not too low) can also be done by the "5x5
square" method. Steps involved are:
1. Write out delta Key on worksheet. (Regular Turingery
procedure.)
2. Assume a character for delta psi prime in the first position
of delta key. This is to be changed later if found wrong. It is actually
assumed to be a slant.
3. Obtain the resultant delta X signs, and carry them forward
throughout the worksheet to their "multiple" positions. At each of these
points assume either a repeat or a complete anti-repeat in delta-psi-prime,
obtaining thereby the delta X for the whole character. A complete delta X
character so obtained is called a "child."
4. Enter on a width of X1 each induced Delta X1 value (from the
children) together with a subscript showing the basic impulse from which it
was induced. (I.e., in the X1 case, subscripts representing impulses 2, 3,
4, or 5.) Values down the columns tend to be alike, if the originally
assumed delta psi prime character ("slant") was correct. But, down a column,
a cross with a subscript 2 for example and a dot with a subscript 3, would
tend to indicate that the signs of the original delta psi prime assumption
were opposite in impulses 2 and 3. A count is therefore made, in each
column, of the number of agreements and disagreements between each possible
pair of subscripts; these counts, for each pair of subscripts, are then totalled
in terms of excesses of agreements or disagreements. The same procedure is
carried out for X2 X3 X4 and X5 widths. The grand total count for each pair
of subscripts, in terms of excesses of agreements or disagreements, is then
entered in a 5x5 flag which is doubled about the diagonal into a 5x5 square.
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