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 ...
The FBI today challenged anyone in the online community to break a cipher code on its site. The code was created by FBI cryptanalysts. The bureau invited hackers to a similar code-cracking challenge ...