code: public static byte[] encodeOctetString(byte[] value)
      {
          byte[] lengthEncoded = encodeLength(value.length);
          ByteArrayDataOutput out = ByteStreams.newDataOutput(2 + lengthEncoded.length + value.length);
          out.write(OCTET_STRING_TAG);
          out.write(lengthEncoded);
          out.write(value);
          return out.toByteArray();
      }
docs: Encodes an octet string.