3Com 2928 User Guide - Page 420

1 PKI Configuration PKI Overview The Public Key Infrastructure (PKI) is a hierarchical framework designed for providing information security through public key technologies and digital certificates and verifying the identities of the digital certificate owners. PKI employs digital certificates, which are bindings of certificate owner identity information and public keys. It allows users to obtain certificates, use certificates, and revoke certificates. By leveraging digital certificates and relevant services like certificate distribution and blacklist publication, PKI supports authenticating the entities involved in communication, and thus guaranteeing the confidentiality, integrity and non-repudiation of data. PKI Terms Digital certificate A digital certificate is a file signed by a certificate authority (CA) that contains a public key and the related user identity information. A simplest digital certificate contains a public key, an entity name, and a digital signature from the CA. Generally, a digital certificate also includes the validity period of the key, the name of the CA and the sequence number of the certificate. A digital certificate must comply with the international standard of ITU-T_X.509. This manual involves two types of certificates: local certificate and CA certificate. A local certificate is a digital certificate signed by a CA for an entity, while a CA certificate, also known as a root certificate, is signed by the CA for itself. CRL An existing certificate may need to be revoked when, for example, the user name changes, the private key leaks, or the user stops the business. Revoking a certificate is to remove the binding of the public key with the user identity information. In PKI, the revocation is made through certificate revocation lists (CRLs). Whenever a certificate is revoked, the CA publishes one or more CRLs to show all certificates that have been revoked. The CRLs contain the serial numbers of all revoked certificates and provide an effective way for checking the validity of certificates. A CA may publish multiple CRLs when the number of revoked certificates is so large that publishing them in a single CRL may degrade network performance. CA policy A CA policy is a set of criteria that a CA follows in processing certificate requests, issuing and revoking certificates, and publishing CRLs. Usually, a CA advertises its policy in the form of certification practice statement (CPS). A CA policy can be acquired through out-of-band means such as phone, disk, and e-mail. As different CAs may use different methods to check the binding of a public key with an entity, make sure that you understand the CA policy before selecting a trusted CA for certificate request. 1-1