Codes and Ciphers by Collins

Author:Collins
Language: eng
Format: epub
Publisher: HarperCollins Publishers
Published: 2013-12-09T16:00:00+00:00

One hundred numbers have been used in this table, so the number of code numbers given to each letter matches its percentage of usage in everyday language. For example, as more than 12 per cent of all letters are ‘e’s, so it has 12 numbers, while j, k, q, v, x and z all score under 1 per cent so only get one letter. This method completely nullifies attack by frequency analysis, but there are other ways to attack such ciphers.

A GLIMMER OF HOPE FOR DECODERS

When trying to break this cipher, the decoder knows that each number can only represent one letter. Once identified, that number will always reveal the presence of the same letter. This can provide clues. For example, if the decipherer was fortunate enough to identify the cipher for ‘q’, this would suggest that the next letter must be ‘u’. Similarly, a three-letter word beginning with ‘a’ is quite likely to be ‘and’. Common two-, three-and four-letter words are listed on page 94. Other spelling-related facts include:

•The high-frequency vowels a, i and o are rarely seen together.

•The most common vowel digraph is ‘ea’.

•The most common repeated letters are:

ss, ee, tt, ff, ll, mm and oo.

•The pairing ‘th’ is common, ‘ht’ is not.

•Indeed, ‘th’ is the most common letter pair, followed by: he, an, in, er, on and re (see also page 93).

•Words are most likely to start with (top five in order):

t, o, a, w, b.

•Words are most likely to end with (top five in order):

e, s, t, d, n.

So the decoder may feel that the rules of spelling and grammar are on their side.

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