# The Newmanry History

## Part of the General Report on Tunny(1945)

### Page 297

Tony Sale's
Codes and Ciphers

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41B Page 297

41 THE FIRST BREAK

41A EARLY TRAFFIC

(a) A first analysis

The first messages on the "Tunny" link ( the name "Tunny" was first given
to this traffic in the summer of 1942) to be studied cryptographically were sent
out shortly after the German invasion of Russia. They passed between Vienna and
Athens. The Hellschreiber method of transmission was used, Some earlier traffic,
sent out in the form of a five-unit code, so it was suspected that a teleprinter
was being used. This was confirmed by a preliminary examination of the later
traffic, which showed that an alphabet of 32 characters was being employed. These
characters were the 26 letters of the normal alphabet, and the six extra symbols
3, 4, 8, 9, + and /.

Each message began with a clear preamble in which there appeared first the
serial number, repeated several times, and then a set of 12 letter, in the form of
name (Anton, Bertha etc.) which was clearly a 12-letter indicator. The symbol 9
was used as a separator in this preamble, and a group of five 9's separated the
clear preamble from the cipher text. Immediately after the cipher text there
appeared a sequence of 8's. The serial number was given in letter form by means of
a simple keyboard substitution the digits 1,2,3,4,5,6,7,8,9,0, being represented
by the letters Q,W,E,R,T,Y,U,I,O,P, respectively.

(b) Meanings of teleprinter letters

On the assumption that a teleprinter machine was being used, two problem
presented themselves. First, was the correlation of the 26 letters of the normal
alphabet with teleprinter signs the same as that of the international convention,
and second, what teleprinter signs corresponded to the symbols 3,4,8,9,+ and / ?

Both these questions were answered by the study of a a series of corrupt
messages which were sent out on July 22nd. Only sixteen different letters
appeared in these messages, and those letters of the normal alphabet which
appeared were those whose first impulse was conventionally a dot. Clearly, owing
to some fault in the machine, the first impulse of each letter had been
transmitted as dot, even when it should have been cross. This effect finally
confirmed the hypothesis that a teleprinter machine was being used and answered
the first of the above questions in the affirmative.

The second problems was then solved by a study of the corrupt clear
preambles. For example the sequence a H / I N R I C H and T H / O 3 O R would be
recognised as corruptions of H E I N R I C H and T H E O D O R respectively. Hence
it would be deduced that for each of the pairs (E,/) and (D, 3) the teleprinter
signs differed only in the first impulse. But by convention E is (x....) and D is
(x..x.). Hence it was deduced that / corresponded to the teleprinter sign
(.....), and 3 to the teleprinter sign (...x.). By this sort of argument the
teleprinter sign corresponding to each of the letters 3, 4, 8, 9, +, and /, were
determined.

41B TUNNY SHOWN TO BE A LETTER SUBTRACTOR

The next advance to be made was the demonstration that the cipher was a
letter subtractor cipher, and the determination of the law of addition used.

This was made possible by the occurrence of a number of "depths of two",
that is, of messages having the same 12 letter indicator, usually the two messages
of such a pair were consecutive, as though an operator had failed to reset his