Certificate signing request
message from an applicant to a certificate authority to apply for a digital identity certificate; lists the public key the certificate should be issued for, identifying information (e.g. domain name) and integrity protection (e.g. digital signature)
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 Certificate Request Message Format (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.
Procedure
Before creating a CSR for an X.509 certificate, the applicant generates a key pair, keeping the private key of that pair secret, e.g.:
The CSR contains information identifying the applicant (such as a distinguished name), the public key chosen by the applicant, and possibly further information. When using the PKCS #10 format, the request must be self-signed using the applicant's private key, which provides proof of possession (POP) of the private key but limits the use of this format to keys that can be used for (some form of) signing.
The CSR must be accompanied by a proof of origin (i.e., proof of identity of the applicant), which is required for security reasons by the certificate authority. The certificate authority may contact the applicant for further information.
Typical information required in a CSR (sample column from sample X.509 certificate).
“Certificate signing request” enters the record as message from an applicant to a certificate authority to apply for a digital identity certificate; lists the public key the certificate should be issued for, identifying information (e.g. domain name) and integrity protection (e.g. digital signature). Crown Archives preserves that source wording while asking what Certificate, signing and request can confirm, complicate or overturn.
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Named sources, stable identifiers and responsible institutions provide the strongest route from overview to verifiable evidence. The source revision retrieved here is dated Mar 5, 2026. The linked authority identifier is Q627554. None of the 0 selected statements returned an explicit reference. The first chronological checks are 1993.
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This entry incorporates text from “Certificate signing request” on English Wikipedia. Contributors are listed in the page history. Text is available under the Creative Commons Attribution-ShareAlike 4.0 License. Selected authority identifiers and statements are retrieved from Wikidata under CC0; their references and qualifiers remain part of the verification path.