Internet X.509 PKI - Certificate Management Message Formats - The document defines message formats to be used between a PKI client and a PKI server or service. The information defined in this document has been absorted into RFC 2510 - Certificate Management Protocols standard. www.imc.org/ietf-pkix
RFC 2511 - Internet X.509 PKI - Certificate Request Message Format - The PKIX standard describes the Certificate Request Message Format (CRMF). This syntax is used to convey a request for a certificate to a Certification Authority (CA) for the purposes of X.509 certificate production. www.imc.org/rfc2511
