Code and ciphers: Julius Caesar, the Enigma and the internet

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solutions to problems
Chapter 4
4.1 (Simple transposition)
If the key length is 6 each column of the transposition box will contain
five letters; we therefore write the cipher text out in columnar form in
Table S.1.
Table S.1
1 2 3 4 5 6
L S L A H I
P C A M O R
E E E H T T
U O M S A M
D E A S R Y
The third line looks as if it might contain the trigraph THE which suggests
that either column 5 or column 6 should be immediately to the left
of column 4. Examination of the other digraphs in 5-4 and 6-4 points to 5-
4 as being more likely. If the ordering 5-4 is correct and the word THE is
present then column 4 must precede column 1, 2 or 3 which doesn’t help
us much at this stage. We therefore look elsewhere and try to find which
column might precede column 5 we see that the only digraph that looks
plausible in row 1 is SH which implies that column 2 should be immediately
to the left of column 5. We therefore have a partial tentative ordering
2-5-4
and if we write out those three columns in that order we have Table S.2.
Table S.2
2 5 4
S H A
C O M
E T H
O A S
E R S
The solution now follows fairly easily. The key is 2 5 4 1 3 6 and the
plaintext, with spaces inserted, is
SHALL I COMPARE THEE TO A SUMMERS DAY.