1 Cyberspace and Cyberspace Security.- 2 Mathematical Preliminaries.- 3. Computational Preliminaries.- 4 Secret-Key Cryptography.- 5 Factoring-Based Cryptography.- 6 Logarithm-Based Cryptography.- 7 Elliptic Curve Cryptography.- 8 Quantum-Safe Cryptography.- 9 Offensive Cryptography.