An Introduction to Cryptography Gianluigi Me
[email protected] Anno Accademico 2011/12 Overview History of Cryptography (and Steganography) Modern Encryption and Decryption Principles Symmetric Key Cryptography Stream Ciphers and Cipher Block Modes Key Management for Conventional Cryptography Attack on Bad Implementation of Cryptography: IEEE 802.11 WEP Message Authentication Public Key Cryptography Digital Signatures Key Management for Public-Key Cryptography Main sources Network Security Essential / Stallings Applied Cryptography / Schneier Handbook of Applied Cryptography / Menezes, van Oorschot, Vanstone Innovative Cryptography, N. Moldovyan , A.Moldovyan Modern Cryptography: Theory and Practice, Wenbo Mao History of Steganography and Cryptography Steganography Steganography Steganos = “covered” in Greek, Graphein = “to write” Being able to communicate secretly has always been considered an advantage Secret messages were often not written down, but rather memorized by sworn messengers Or hidden Demaratus, a Greek immigrant to Persia, reveals Persia’s intention to attack Athens. Writes the secret message on a tablet, and covers it with wax. Histaiaeus encourages Aristagoras of Miletus to revolt against the Persian King. Writes message on shaved head of the messenger, and sends him after his hair grew Chinese wrote on silk, turned into wax-covered ball that was swallowed by the messenger Steganography (cont.) Invisible Ink Certain organic fluids are transparent when dried but the deposit can be charred