How to Solve a Number Cipher

How to Solve a Number Cipher
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It’s easy to solve number ciphers if you know the trick: some letters are more frequent in the English language than others. That means solving a cypher is usually a matter of looking for high frequency letters and taking educated guesses. Solving number cyphers is possible, but time consuming: it requires a great deal of patience, especially with ciphers under 200 words.

    Count how many times each number appears in your cipher. You may be able to spot patterns. For example, e is an extremely high frequency letter; it will appear an average of 26 times in a 200-word cipher while q and z appear on average less than once per 200 words.

    Write a contact table. A contact table is a way to visually see how letters relate to each other. David Kahn suggests the first step to making a contact table is to write the numbers 1 through 26 in descending order on a page, one number per line.

    Write 26 numbers horizontally next to each descending number: 1 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 2 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 3 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 through 26 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26

    Starting with the first number, 1, identify which numbers come before it, and which come after it. Put a tally mark before the number or after it in your table each time you count a letter. For example, if part of your cypher is 131419, the tally marks would be as follows: 1 1 2 |3| |4| 5 6 7 8 9| 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26

    Repeat Step 4 for all numbers in your cypher.

    Identify common vowels. According to Kahn, the letter e will be as easy to spot as a "6 1/2-feet tall man at a costume party." It will be the most frequent number (Step 1) and it will have the largest spread, appearing next to every other number more times than the other numbers. The letters a, i, and o are also frequent, but they don't often appear next to each other in number cyphers--so look for three frequently appearing numbers that don't appear next to each other. The letter combination io is the only exception: It is fairly common so look for that combination.

    Identify the high frequency consonants in in your frequency table. According to Kahn, n will be easy to find because four-fifths of the letters that precede it will be vowels. Y comes after n (or sometimes e) but never before it. Look for the other common letters r and s.

    Insert your findings into the cipher to give you a partial solution. You should be able to identify the rest of the cipher from this start.

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