Security at the Application Layer: Email architecture, PGP (Pretty Good Privacy), S/MIME. Security at the Transport Layer (SSL and TLS): SSL architecture, Four protocols, SSL message formats, Transport Layer Security, Secure Electronic Transaction. Security at the Network Layer (IPSec) : Two modes, Two Security protocols, Security Association, Security Policy, Internet Key Exchange, ISAKMP. Intruder: Intruder, Intrusion Detection, Password Management. Malicious Software : Viruses and Related Threats, Virus Countermeasures, Distributed Denail of Service Attack. Firewall : Firewall Design Principles, Trusted systems, Common Criteria for Information Technology Security Evaluation. Authentication : Kerberos V4 and V5, X.509 Authentication Service, Public Key Infrastructure. Physical Layer Security:Shannon’s perfect secrecy, Secure Communication over Noisy Channel, Channel Coding for Secrecy, Secret Key Agreement from noisy observation, Active attacks, Physical Layer Security and Classical Cryptography.