## Department of Computer Science, Unit Catalogue 2008/09

#### CM30173 Cryptography

 Credits: 6
 Level: Honours
 Semester: 2
 Assessment: EX 100%
 Requisites:
 Before taking this unit students must have an elementary knowledge of number theory, as in Chapters 1-2 of Davenport The Higher Arithmetic, or have taken either CM10139 Computation I : numbers & structures, or MA10001 Numbers.
 Aims & Learning Objectives: Aims: To introduce students to the techniques, tools and pitfalls of cryptography (including authentication etc.)Objectives: Students will understand the basic mathematics behind private-key and public-key cryptography. Students will be able to describe several well-known techniques for cryptographic security and authentication. Content: Introduction to the problem: security, privacy, authentication, repudiation, revocation. The key distribution problem: public vs private keys. The mathematics of crytography: Fermat-Euler Theorem, structure of finite fields and elliptic curves. Crytographicalgorithms: Diffie-Hellman, RSAi, El-Gamal. Cryptanalysis: discrete logarithms, factoring. The Coppersmith attack. Elliptic Curve analogues. Private-key algorithms: DES, 3DES and AES. Good hashing algorithms: MD5, SHA-1. Characteristics of safe keys, using cryptography: digital signatures: how to find the public key. Repudiation and revocation, examples in practice: PGP, digital certificates.