private X509CertificateStructure(
            Asn1Sequence seq)
        {
            if (seq.Count != 3)
                throw new ArgumentException("sequence wrong size for a certificate", "seq");

            //
            // correct x509 certficate
            //
            tbsCert = TbsCertificateStructure.GetInstance(seq[0]);
            sigAlgID = AlgorithmIdentifier.GetInstance(seq[1]);
            sig = DerBitString.GetInstance(seq[2]);
        }
        public X509CertificateStructure(
            TbsCertificateStructure	tbsCert,
            AlgorithmIdentifier		sigAlgID,
            DerBitString			sig)
        {
            if (tbsCert == null)
                throw new ArgumentNullException("tbsCert");
            if (sigAlgID == null)
                throw new ArgumentNullException("sigAlgID");
            if (sig == null)
                throw new ArgumentNullException("sig");

            this.tbsCert = tbsCert;
            this.sigAlgID = sigAlgID;
            this.sig = sig;
        }