# The 1944 Bletchley Park Cryptographic Dictionary

### Page 12

Tony Sale's
Codes and Ciphers

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(continued)

As the shape is completely determined by the key-length and the number of letters in the message the recipient, knowing the key, can reconstruct the cage, and the cryptographer, knowing only the number of letters, can make tentative cages for different assumed key-lengths.

2. A Playfair square.

CALL SIGN :

A group usually of three or more letters and/or figures, sent either in clear or in cipher, either in the preamble or in the body of a message, and serving to identify the sender and/or the recipient; a code name.

CARRY :

1. To represent or convey.

2. (in addition, etc: see carrying)

CARRYING :

Belonging to or obtained in conformity with the rules of normal adding and subtracting (whereby 9 + 7 = 16, 33 - 18 = 15), as opposed to normal cryptographic addition and subtracting (whereby 9 + 7 = 6, 33 - 18 = 25), which is non-carrying.

CATALOGUE :

(especially). A tabulated record of all the immediately relevant consequences or implications of each of a complete set of hypotheses in a consultable form.

CENTIBAN :

A scoring unit for probabilities equal to one-hundredth of the true scoring unit, enabling decimal fractions to be expressed more conveniently as whole numbers. The true score (i.e. the logarithm of the probability of a particular occurrence) multiplied by one hundred is the score expressed in centibans, cf. deciban.

CHAIN :

1. (in double Playfair). A series of non-reversible bigram equations such that the clear bigram of one equation is the reverse of the cipher bigram in the previous. From such a series it can be inferred that the letters forming every second bigram (either of the clear bigrams or of the cipher) occur in the same line in their respective squares, and are evenly spaced along that line.

2. (especially in Enigma). A connected series of constatations forming a menu or part of a menu; also, a set of consequences obtained from one stecker assumption.

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