159
The frequency of letters occurring in a long piece of text has a characteristic pattern. The ordering of letters, with the most frequent first, is always similar to [1]
ETAONRISHDLFCMUGPYWBVKXJQZ.
By generating a frequency list for the numbers in the diary and comparing with this list, it should be possible to match numbers with letters. So I hurried off to my computer, typed in the first page of numbers and wrote a little program to determine the frequency of each number. Setting 1=A, 2=B, etc., the ordering derived from this first page was
ETAONRISHLDUFWPCMGYBXVKJZQ.
With the first nine letters of the two lists in the same order, and only minor variations thereafter, the only conclusion was that there was a direct translation of numbers to letters with no change of ordering. This also confirmed that the numbers did correspond in some way to text but that the method used was not a substitution cipher.
What Next? Now that the translation of numbers into letters had been determined, the next question was how should the letters be rearranged to give meaningful text. The number of possible ways in which such a transposition cipher could be done made the problem seem a little less easy than my early optimism had led me to believe. So I returned to the pages of the diary looking for more clues. There was very little in the way of markings on any of the pages apart from the first. However, the following observations invited further investigation.
•
In the right-hand margin of the first page, there was a right-hand arrow with the number 340 next to it and a down arrow with the number 330 next to it.
Some numbers on the first few lines had a box around them.
To the left of some lines throughout the diary was the number zero. On such lines, there was always a column containing four zeros which seemed to be some sort of marker (see Fig. 1).
The numbers with a box around them seemed a good place to begin. Starting at the top of the first page, the position of the first few
159
The frequency of letters occurring in a long piece of text has a characteristic pattern. The ordering of letters, with the most frequent first, is always similar to [1]
ETAONRISHDLFCMUGPYWBVKXJQZ.
By generating a frequency list for the numbers in the diary and comparing with this list, it should be possible to match numbers with letters. So I hurried off to my computer, typed in the first page of num- bers and wrote a little program to determine the frequency of each number. Setting 1=A, 2=B.etc., the ordering derived from this first page was
ETAONRISHLDUFWPCMGYBXVKJZQ.
With the first nine letters of the two lists in the same order, and only minor variations thereafter, the only conclusion was that there was a direct translation of numbers to letters with no change of ordering. This also confirmed that the numbers did correspond in some way to text but that the method used was not a substitution cipher.
What Next? Now that the translation of numbers into letters had been determined, the next question was how should the letters be rear- ranged to give meaningful text. The number of possible ways in which such a transposition cipher could be done made the problem seem a little less easy than my early optimism had lead me to believe. So l returned to the pages of the diary looking for more clues. There was very little in the way of markings on any of the pages apart from the first. However, the following observations invited further investigation.
•
In the right hand margin of the first page, there was a right hand arrow with the number 340 next to it and a down arrow with the number 330 next to it.
Some numbers on the first few lines had a box around them.
To the left of some lines throughout the diary was the number zero. On such lines there was always a column containing four zeros which seemed to be some sort of marker (see Fig. 1).
The numbers with a box around them seemed a good place to begin. Starting at the top of the first page, the position of the first few
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