PKIX

IETF-PKIX Public-Key Infrastructure X.509 Working Group Charter
Charter of the working group that develops Internet standards needed to support an X.509-based PKI. (pkix)
http://www.ietf.org/html.charters/pkix-charter.html

RFC 2527 - Internet X.509 PKI - Certificate Policy and Certification Practices Framework
The document presents a framework to assist the writers of certificate policies or certification practice statements forcertification authorities and public key infrastructures.
http://tools.ietf.org/html/rfc2527

RFC 2528 - Representation of Key Exchange Algorithm (KEA) Keys in Internet X.509 PKI Certificates
The PKIX specification profiles the format and semantics of fields in X.509 V3 certificates containing Key Exchange Algorithm (KEA) keys, a classified algorithm for exchanging keys.
http://tools.ietf.org/html/rfc2528