Periodicity is the repetition of a certain sequence of characters of length k (k >= 1) from a certain position in the document the offset. The periodicity must continue through to the end of the document. Therefore it is not enough that a patterns appears multiple times in a file to be a period.
All periodic cycles are shown. It is only possible to have several cycles when they are nested within each other.
A document with k cycles must be at least 2 ^ (k + 1) – 2 bytes long. CrypTool can find at most 100 periodic cycles.
The first byte of the document has the offset value 1.
The periodicity analysis can be applied to text and binary documents.
Examples:
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cycle a has offset 5 and period length 1. |
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cycle az has offset 4 and period length 2. |
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contains two nested cycles, the first with offset 3 and period length 5 (bazaz ) and the second with offset 9 and length 2 (az ). |
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is not a period |
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is not a period |
An analysis of periodicity can only be carried out if the length of the document is at least 2 bytes.
The display can be stored in a text file if required.
If the cycle is longer than 20 characters, then only the first 20 characters of a cycle will be displayed.