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Information about Public Key Certificates

A Public Key Certificate is a data record holding some form of identification about you, a server or a Certificate Authority and the public key you or the one whose certificate it is, are using. You may have several certificates issued for yourself, each for a different public key (and associated private Key).

Public Key Certificates assume that the private key of the entity that issued the certificate is not compromised (that is, unavailable to unauthorized individual) and that the same holds for the private key (yours) whose public component it certifies.

A certificate is signed by a Certificate Authority using its private key. All certificates are valid in a restricted period of time, generally a year, possibly more if the keys are considered safe. Certificate Authority keys are generally valid for years, even decades.

Opera supports two kinds of Public Key Certificates: personal certificates issued to yourself, and Certificate Authority certificates issued by the CA's to themselves or to other CA's. The third kind, server certificates, are only used to authenticate the server.

A Personal Certifiate is issued by a Certificate Authority to you as an individual, Opera is not able to install personal certificates already issued to another browser, as it is unable to retrieve the Private key associated with the certificate. The installed certificates are listed in the Tools > Preferences > Advanced > Security > Manage certificates dialog box (Mac: Opera > Preferences > Advanced > Security > Manage certificates), under the "Personal" tab.

The Certificate Authority certificates are used to verify the correctness of received server certificates, and to build the sequence of certificates a client can send the server when it request a certificate. These certificates may be signed by another CA certificate, or be selfsigned, that is, it holds the CA's public key, and is signed with the corresponding private key. These certificates are listed in the "Manage certificates" dialog box (see above), under the "Authorities" tab, where you may select actions to be taken when a server sends a certificate that is signed directly or indirectly by the given CA; you may select to break the connection, or ask for user confirmation before continuing.

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