Jeri Freedman 
Famous Cryptographers [PDF ebook] 

The stories of some of the individuals who have shaped cryptography are engagingly told in this narrative. Readers consider Polybius and his cipher (the Polybius square), Julius Caesar and his secret military ciphers, diplomat Blaise de Vigenere and his polyalphabetic cipher, Antoine Rossignol, the "Black Chamber, " and the Great Cipher he developed for Louis XIV, Anson Stager and Civil War cryptography, and cryptanalyst Agnes Meyer Driscoll, codenamed Madame X, who decrypted radio codes for the US government during both world wars. Elizebeth Friedman, Alan Turing, Whitfield Diffie, Martin Hellman, and Ralph Merkle and their cryptographic methods are also examined.