A CRL is a list identifying revokedĬertificates, which is signed by a CA and made freely available at a public distribution point. This method involves each CA periodically issuing a signed data structure called a certificate revocation list (CRL). There are several mechanisms to represent revocation information. Under such circumstances, the issuing CA needs to revoke the certificate. Such circumstances includeĬhange of name (for example, requiring to change the subject of a certificate due to an employee’s change of name), change of association between subject and CA (for example, when an employee terminates employment with an organization), and compromise or suspectedĬompromise of the corresponding private key. However, various circumstances may cause a certificate to become invalid prior to the expiration of the validity period. Once issued, a certificateīecomes valid when its validity time has been reached, and it is considered valid until its expiration date. For example, a certificate may be issued with a validity of one day, thirty years, or even longer. Without checking certificates for revocation, the possibility exists that an application or user will accept credentials that have been revoked by a CA administrator.Ĭertificates are issued with a planned lifetime, which is defined through a validity start time and an explicit expiration date. Instead, clients connect to alternate resources, such as Web servers or Lightweightĭirectory Access Protocol (LDAP) directories, where the CA has published its revocation information. Traditionally,Ī PKI uses a distributed method of verification so that the clients do not have to contact the Certification Authority (CA) directly to validate the credentials presented. For certificate status to be determined, public key infrastructure (PKI) certificate revocation information must be made available to individuals, computers, network devices, and applications attempting to verify the validity of certificates.
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