[JoGu]

Cryptology

I.2 Polyalphabetic Ciphers

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Contents

  1. Key alphabets
  2. The invention of the polyalphabetic substitution [mathematical description as PDF]
  3. Tools for polyalphabetic substitution
  4. Mathematical description of the periodic polyalphabetic substitution [PDF]
  5. The cipher disk algorithm [PDF]—
    with Perl programs for encryption and decryption
    [online by web forms: encryption, decryption]
  6. Analysis of periods
    with Perl program [online by web form]
  7. Cryptanalysis of a polyalphabetic ciphertext (German plaintext)—
    finding the period by repetition search and column analysis
  8. Rearranging the columns [PDF]
  9. Summary

Here is the mathematical part as a single PDF, with an appendix: The Birthday Paradox.


Author: Klaus Pommerening, 1999-Oct-18; last change: 2021-Jan-14.