Cryptology I.7 Aperiodic Polyalphabetic Ciphers

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Contents

1. Running-Text Ciphers [mathematical version]
2. Cryptanalytic Approaches to Running-Text Ciphers [mathematical version]
3. Cryptanalysis According to FRIEDMAN
4. Other Applications of Running-Text Analysis [mathematical version]
5. Random Keys [mathematical version]
6. Autokey Ciphers [mathematical version]
7. Example: Cryptanalysis of an Autokey Cipher
8. Similarity of Ciphers [mathematical version only]

Here is the complete mathematical part as PDF.

Overview Over Polyalphabetic Ciphers

[*] Not completely exact. The running-text cipher is only one (although the most important) special case of an aperiodic polyalphabetic substitution using the standard alphabet. An analogous statement holds for PORTA's disk cipher and a general periodic polyalphabetic substitution. In contrast by stream cipher we denote an even more general construct.