Contents: 1 History and Basic Cryptographic Concepts 2 Protocols, Discrete Log, and Diffie-Hellman 3 Public-Key Cryptography 4 Probabilistic Primality Tests 5 Factoring 6 Security of RSA 7 Authentication 8 Key Management 9 Applications and the Future Appendix A: Letter Frequency Analysis Appendix B: Elementary Complexity Theory Appendix C: Fundamental Facts Solutions to O…