Letters frequency Analysis Tool


Letters frequency analysis :

Frequency analysis is a commonly used technique in domain such as cryptanalysis. The most ancient description for what we know was made by Al-Kindi, dating back to the IXth century. The letter frequency analysis was made to decrypt ciphers such as monoalphabetical ciphers, for instance Caesar cipher, which means that frequency analysis could have been used before Al-Kindi.

This tool allow you to analyse frequency of letters in any text you want. It counts all the letters, digraphs, trigraphs and quadrigraphs and print a chart with all the data. Once you got the frequency for each letter (or digraphs, trigraphs, quadrigraphs), you have to compare it to language letters frequency. In the options you can print a chart with different languages letters frequencies, if I have the data. If I don't have the frequencies, try to search for it on internet. For now I have frequencies charts for english, french, german, italian, spanish and portuguese.

On the options you also can include into the frequency analysis all the caracters or only the numbers. When you try to decrypt a cipher using this tool, keep in mind that your text may be too short to really find a pertinent frequency analysis, you should then try to compare it with different letters. For instance in english the letters that you'll find the most are e, t, a ,o, i, n. If your cipher frequencies are for instance h, d, w, q, l, u, try to match h with e, d with t, w with a, q with l, u with n. It will not be a good match if your cipher was too short, so then try another match, for instance d for a instead of t, try different things until you find the good match.
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