• PKI tutorial by Peter Gutmann
• PKIX workgroup
• Easing the PAIN Lưu trữ 2005-04-08 tại Wayback Machine — a detailed explanation of PKI Privacy, Authentication, Integrity and Non-repudiation (PAIN)
• NIST PKI Program — in which the National Institute of Standards and Technology (NIST) is attempting to develop a public key infrastructure
• Mozilla Open Source PKI Projects
• NewPKI Lưu trữ 2006-03-14 tại Wayback Machine — a PKI based on the OpenSSL low-level API

Cung cấp chứng thực số tự động

OpenPGP

• cardboard.net llc[liên kết hỏng] "currently broken"
• Imperial Violet (Adam Langley) Lưu trữ 2005-03-19 tại Wayback Machine
• Robot Certificate Authority, at JamesHoward.us
• Toehold (Kyle Hasselbacher) Lưu trữ 2005-11-24 tại Wayback Machine
• signedtimestamp.org Lưu trữ 2006-05-19 tại Wayback Machine
• PGP Corporation

SSL

• Ascertia PVT Ltd Free Certificates Lưu trữ 2005-11-25 tại Wayback Machine
• CAcert.org
• CertifyID Certificates[liên kết hỏng]
• Thawte.com 123 SSL Certificates
• Geotrust QuickSSL Certificates
• Godaddy Turbo SSL Certificates
• Comodo SSL Certificates
• DigiCert SSL Certificates
• VeriSign SSL Certificates