byte[] hiddenPlusLength = Util.fromInt(0);
if (hidden.length > 0) {
hiddenPlusLength = Util.lenPrefix(hidden);
}
stream.updateSign(ByteBuffer.wrap(blob));
stream.updateSign(ByteBuffer.wrap(hiddenPlusLength));
stream.updateSign(ByteBuffer.wrap(FORMAT_BYTES));
// now get signature output
ByteBuffer output = ByteBuffer.allocate(stream.digestSize());