From the riddles of ancient Egypt to cryptography in the Renaissance - 3500 years in the making -- From sixteenth-century cryptography to the new millennium - the last 500 years -- Symmetric-key cryptography -- Public-key cryptography -- Cryptographic protocols -- Key management -- Message authentication -- Electronic mail and internet security -- Applications and the future -- Noncryptographic security issues -- Information theory and coding -- Appendix A: Mathematical facts -- Appendix B: Pseudorandom number generation -- Appendix C: Factoring large integers -- Appendix D: Technical and advanced details -- Appendix E: Probability theory -- Appendix F: Recognizing primes -- Appendix G: Exercises.