In the winter of 54 BCE, a javelin flew into a besieged Roman camp in Gaul with a letter tied to it. The camp was commanded by Quintus Tullius Cicero, brother of the famous orator, and enemy forces ...

Introduction to ciphers and substitution. Alice and Bob and Carl and Julius: terminology and Caesar Cipher ; The key to the matter: generalizing the Caesar Cipher ; Multiplicative ciphers ; Affine ...

1. Introduction -- 2. From Julius Caesar to simple substitution -- 3. Polyalphabetic systems -- 4. Jigsaw ciphers -- 5. Two-letter ciphers -- 6. Codes -- 7. Ciphers for spies -- 8. Producing random ...

plaintext AND to decrypt a ciphertext. That is four operations, and most resources show one. Every sheet here does all four. 8-bit ASCII code is given, and so is the one-time pad’s; the student poses ...