Poly-alphabetic Substitution Cipher

Tags

cryptography

A Substitution Cipher in which each character of the input doesn't necessarily always map to the same character.

For example a cipher built using [see page 12, multiple] ceaser-ciphers where: Each characters position in the input leads to it being passed to a different cipher (for example characters with odd cardinality get passed through a ceaser-cipher with offset 5 but those with an even cardinality get passed through one with an offset 13). In this compound-cipher it's possible for a character A to map to F and to map to N depending on its position in the input.

This isn't quite as effective if the cracker can work out the period of reuse of particular ciphers, but the idea of changing ciphers for different characters is a good one.