Pt. I. Concepts. 1. Introduction. 2. Public-Key Cryptography. 3. The Concept of an Infrastructure. 4. Core PKI Services: Authentication, Integrity, and Confidentiality. 5. PKI-Enabled Services. 6. Certificates and Certification. 7. Key and Certificate Management. 8. Certificate Revocation. 9. Trust Models. 10. Multiple Certificates per Entity. 11. PKI Information Dissemination: Repositories and Other Techniques. 12. PKI Operational Considerations. 13. Electronic Signature Legislation and Considerations. 14. PKI in Practice. 15. The Future of PKI. 16. Conclusions and Further Reading -- Pt. II. Standards. 17. Introduction. 18. Major Standards Activities. 19. Standardization Status and Road Map. 20. Standards: Necessary but Not Sufficient. 21. Conclusions and Further Reading -- Pt. III. Deployment Considerations. 22. Introduction. 23. Benefits and Costs of a PKI. 24. Deployment Issues and Decisions. 25. Barriers to Deployment. 26. Typical Business Models