Certificate signing request

In public key infrastructure (PKI) systems, a certificate signing request (CSR or certification request) is a message sent from an applicant to a certificate authority of the public key infrastructure (PKI) in order to apply for a digital identity certificate. The CSR usually contains the public key for which the certificate should be issued, identifying information (such as a holder or domain name) and a proof of possession of the corresponding private key (typically in the form of a digital signature, which includes integrity protection). The most common format for CSRs is the PKCS #10 specification, first published in November 1993; others include the more capable (CRMF) and the SPKAC (Signed Public Key and Challenge) format generated by some web browsers.

Note that neither of the CSR formats authenticate the identity of the requester. The proof of origin of the request must be achieved and verified by other means (typically using a certificate enrollment protocol such as CMP, EST, or ACME), otherwise the obtained certificate has no real security value.