code: public void encode(DerOutputStream out) throws IOException {
  
          DerOutputStream tmp = new DerOutputStream();
          hashAlgId.encode(tmp);
          tmp.putOctetString(issuerNameHash);
          tmp.putOctetString(issuerKeyHash);
          certSerialNumber.encode(tmp);
          out.write(DerValue.tag_Sequence, tmp);
  
          if (debug) {
              HexDumpEncoder encoder = new HexDumpEncoder();
              System.out.println("Encoded certId is " +
                  encoder.encode(out.toByteArray()));
          }
      }
docs: Encode the CertId using ASN.1 DER.
  The hash algorithm used is SHA-1.