Introduction to the principles of number theory and the practice of network security and cryptographic algorithms. Topics include: Divisibility and the Greatest Common Divisor, Euclidean Algorithm, modular arithmetic and discrete logarithm, Primes, primality testing, Chinese Remainder Theorem. Conventional or Symmetric Cryptography (Rijndael, AES family), Modes of operation, Public or Asymmetric Cryptography (RSA), key management and exchange, hash functions (MD5, SHA family, HMAC), digital signatures, certificates and authentication protocols (X.509, DSS, Kerberos), electronic mail security (PGP), web security and protocols for secure electronic commerce (IPSec, SSL/TLS, SET).