Running key cipher: Difference between revisions

Revision as of 11:09, 2 June 2008

Revision as of 13:26, 18 June 2009

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{{unreferenced|date=June 2009}}

In classical [[cryptography]], the '''running key cipher''' is a type of [[polyalphabetic substitution|polyalphabetic]] [[substitution cipher|substitution]] [[cipher]] in which a text, typically from a book, is used to provide a very long [[keystream]]. Usually, the book to be used would be agreed ahead of time, while the passage to use would be chosen [[random]]ly for each message and secretly indicated somewhere in the message.