polyalphabetic

More complex forms of encryption, like the polyalphabetic Vigenère cipher, can also make use of (potentially much longer) keywords or phrases as the basis of their cryptographic keys.

A Quick Fringe Cipher Follow-Up 2009

He conceived of it as a campus-wide competition during the Independent Activity Period - four weeks each January when the school gives students the freedom to explore creative projects - and wrote up puzzles that involved such things as breaking a polyalphabetic cipher and translating a Chinese ideogram.

Boston.com Top Stories 2011

These are encrypted with a simple polyalphabetic cipher , for those who care, but are very easy to open.

Ars Technica Ben Kuchera 2011

The simplest polyalphabetic substitution used multiple constant shift keys.

Citizendium, the Citizens' Compendium - Recent changes [en] Howard C. Berkowitz 2010

The first two tests mentioned both address the problem of determining the number of key alphabets used in a polyalphabetic cipher.

Citizendium, the Citizens' Compendium - Recent changes [en] Howard C. Berkowitz 2010

Even with a method that was a short-period polyalphabetic solution, cryptographers might use different techniques for putting letters into the encryption system, and removing them.

Citizendium, the Citizens' Compendium - Recent changes [en] Howard C. Berkowitz 2010

When the frequency of letters, graphed by frequency against count, do not follow the curve characteristic to the language, which becomes increasingly effective when keys become more complex, even in simply polyalphabetic substitution on a monographic cipher, such as the Vigenere method.

Citizendium, the Citizens' Compendium - Recent changes [en] Howard C. Berkowitz 2010

Both were designed at a time when polyalphabetic substitution was primarily a manual process, so they work best when there are both a relatively small number of key alphabets. an algorithm in which the key alphabets are used in a straightforward repeating sequence (e.g., 12341234, not 42231431) and a relatively large amount of text encrypted in them.

Citizendium, the Citizens' Compendium - Recent changes [en] Howard C. Berkowitz 2010

Result of polyalphabetic substitution (four Caesar based used)

Citizendium, the Citizens' Compendium - Recent changes [en] Howard C. Berkowitz 2010

Even with a method that was fundamentally polyalphabetic solution, cryptographers might use different techniques for putting letters into the encryption system, and removing them.

Citizendium, the Citizens' Compendium - Recent changes [en] Howard C. Berkowitz 2010