Cryptology I.1 Monoalphabetic Ciphers

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Contents

1. Ciphers and Their Mathematical Description
2. Shift Ciphers and Their Mathematical Description, ROT13, XOR
3. Cryptanalysis of Shift Ciphers (exhaustion)
4. Monoalphabetic Substitution and Its Mathematical Description—
   encryption and decryption via web forms
5. Algorithms and Programming in Perl (with crash course)
6. Cryptanalysis of Monoalphabetic Substitution (approaches)
7. Statistical Analysis of Ciphertext—
   letter frequencies in German, English, French, Russian and some other languages, letter frequencies in MS-Word [PDF],
   Perl programm for counting single letters [online] or bigrams [online]
8. Example of a Statistical Cryptanalysis (in German).
   For an example in English see Excerpt from Poe's Gold-Bug.
9. Pattern Search with Program in Perl [mathematical background] [online: search in dictionary or text]
10. Example of a Pattern Search
11. Known Plaintext Attack
12. Early History of Cryptology
13. Variants of Cryptographic Procedures [mathematical version], Polygraphic Substitutions, and Codebooks

Here is the mathematical part as a single PDF, with appendices: Mathematical Excursion to Permutations and STIRLINGs Formula