Introduction - Attacks, services and mechanisms - Classical encryption techniques - DES-Block cipher - Design principles and modes of operation. Encryption Algorithms - Hash functions - Triple DES - RC5 - Key management – Public key cryptography - RSA algorithm - Digital signatures and authentication protocols. System Security - Backups - integrity management - protecting against programmed threats, viruses and worms - physical security - Personnel security. Network security - Protection against eavesdropping - Security for modems - IP security - Web security - Electronic mail security - Authentication applications. Security tools-Firewalls-Wrappers-proxies-Discovering a break-in Denial of services attacks and solutions - Cryptographic security tools: Kerberos, PGP, SSH, SRP, OPIE.