CSE425 Cryptography

Graham Farr

Prohibitions: CSE447.

The subject consists of two parts: a more general introduction to basic concepts in cryptography as a first part and an in-depth discussion of selected cryptographic protocols in the second part.

The first part consists of: Elementary secret-key cryptosystems (transposition, substitution, polyalphabetic, etc.), basic principles of building and combining them, a modern secret-key cryptosystem such as the Data Encryption Standard. One-way functions and public-key cryptosystems, trapdoor functions, relevant notions from computational complexity, specific systems including: Diffie-Hellman key exchange scheme, RSA, ElGamal. Comparison of secret- and public-key cryptography.

The second part covers: Entropy, information, sources, coding: theory and application to elementary secret-key cryptosystems; language as a source; unicity point; perfect secrecy. Cryptographic protocols: authentication (secret- and public-key) and digital signatures; further applications of one-way functions and public-key cryptosystems, such as bit-commitment and relatives; more advanced protocols, e.g. electronic cash, interactive proofs.

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