http://www.rfc-editor.org/rfc/rfc4043.txt
RFC 4043: Internet X.509 Public Key Infrastructure Permanent Identifier, D. Pinkas, T. Gindin2005-05-01T23:00:00-00:00The subject name, carried in the subject field, is only unique for each subject entity certified by the one CA as defined by the issuer name field. However, the new name form can carry a name that is unique for each subject entity certified by a CA. [STANDARDS-TRACK]