This class helps to support crossCerfificatePairs in a LDAP directory according RFC 2587

    crossCertificatePairATTRIBUTE::={
      WITH SYNTAX   CertificatePair
      EQUALITY MATCHING RULE certificatePairExactMatch
      ID joint-iso-ccitt(2) ds(5) attributeType(4) crossCertificatePair(40)}

The forward elements of the crossCertificatePair attribute of a CA's directory entry shall be used to store all, except self-issued certificates issued to this CA. Optionally, the reverse elements of the crossCertificatePair attribute, of a CA's directory entry may contain a subset of certificates issued by this CA to other CAs. When both the forward and the reverse elements are present in a single attribute value, issuer name in one certificate shall match the subject name in the other and vice versa, and the subject public key in one certificate shall be capable of verifying the digital signature on the other certificate and vice versa. When a reverse element is present, the forward element value and the reverse element value need not be stored in the same attribute value; in other words, they can be stored in either a single attribute value or two attribute values.

      CertificatePair ::= SEQUENCE {
        forward        [0]    Certificate OPTIONAL,
        reverse        [1]    Certificate OPTIONAL,
        -- at least one of the pair shall be present -- } 

      CertificatePair ::= SEQUENCE {
        forward        [0]    Certificate OPTIONAL,
        reverse        [1]    Certificate OPTIONAL,
        -- at least one of the pair shall be present -- }

      CertificatePair ::= SEQUENCE {
        forward        [0]    Certificate OPTIONAL,
        reverse        [1]    Certificate OPTIONAL,
        -- at least one of the pair shall be present -- }