Fundamentals: Substitution Ciphers, Transpositions (Permutations), block ciphers, stream ciphers. Public-key cryptography.  The Uses of Encryption: Cryptographic Hash Functions, Key Exchange, Digital Signatures, digital certificates. Mathematics  for Cryptography:  NP- Complete   Problems;  Inherently  Hard  Problems;   Inverses  (Fermat's  Theorem),   Primes, Greatest Common Divisor (Euclidean Algorithm), Modular Arithmetic.