public X509CertificateStructure(ASN1Sequence seq) {
    this.seq = seq;

    //
    // correct x509 certficate
    //
    if (seq.size() == 3) {
      tbsCert = TBSCertificateStructure.getInstance(seq.getObjectAt(0));
      sigAlgId = AlgorithmIdentifier.getInstance(seq.getObjectAt(1));

      sig = (DERBitString) seq.getObjectAt(2);
    }
  }