Thanks folks That is what I was looking for.

Thanks !! I just figured it out after reading Docs !! Thanks for replying (y)

I’ve found out what my issue was. I was reading binary files, and char arrays end at null characters ('\0'), which binary files may have. I found out that I can use a QByteArray all the way instead of an array of chars, resulting in a more readable that works regardless of the null characters in the binary file: const qint64 CHUNK_SIZE = 9728000; ioDevice.seek(0); QByteArray data = ioDevice.read(CHUNK_SIZE); QByteArray hash = QCryptographicHash::hash(data, QCryptographicHash::Md4); std::cout << "ioDevice.read() hash: " << hash.toHex().toStdString() << std::endl;