Here are some suggested web sites and other resources for learning about Public Key Infrastructure (PKI).

Short vendor produced introductions to cryptography and public key infrastructure can be found at:

• Entrust:An Introduction to Cryptography and Digital Signatures (PDF)
• VeriSign/Netscape: Understanding PKI

A PKI Policy White paper (PDF) is available from Digital Signature Trust.

Some of the vendors have extensive white paper collections on their websites.
Here are links to some of them:

• Entrust White Papers
• VeriSign White Papers
• RSA Labs: Home of the PKCS specifications, Crypto FAQ, Factoring Challenges, and more.

See the PKI vendor's web sites to explore other topics. (pointers found on the "Vendors" page)

The National Institute of Standards and Technology (NIST) is a leader in the development of a Federal Public Key Infrastructure that supports digital signatures and other public key-enabled security services. NIST is coordinating with industry and technical groups developing PKI technology to foster interoperability of PKI products and projects. The main web site is here: NIST PKI Program

The Internet Engineering Task Force (IETF) publishes useful information on standards and best practices in RFCs.