Combine certificates and cryptographic keys into identities.
An identity consists of a private key packaged with the certificate that contains and vouches for the corresponding public key. You use the certificate, key, and trust services API to create an identity from a private key and its certificate, or to import an identity from a password-protected PKCS #12 file. You then use the API to extract the key and certificate from the identity. You can also use the keychain services API to store the identity to or retrieve it from a keychain, much as you would the certificate or key by itself.