What is the best way to encrypt large binary data using QCA

[ngendlio]

Hello everyone ! I hope you're having a nice day!
In fact, I was to using the QCA library in Qt , and everything works great except when I want to encrypt large files ....
When i try to encrypt large files that are binary , the output is really small.. I don't understand why ?
I dont 't know if it is teh problem of my code
For example , look at my code, I do not know if anyone could give me an example of a project that I can use as a reference

void AESCrypt::writeBinary(QByteArray arr, QString filePath)
{
    QFile f(filePath);
    qDebug()<<" Transfering to new File"+f.fileName();
    
    if(!f.open(QIODevice::WriteOnly|QIODevice::Truncate)){
        qDebug()<<" Failed to Write to the file "+filePath+"__>"+f.errorString();return;
    }
    //    QDataStream out(&f);
    //    out.setByteOrder(QDataStream::LittleEndian); // *** set little endian byte order
    //    out<<arr;
    f.write(arr);
    qDebug()<<" J ai ecrit "+QString::number(arr.size())+" "+hash(arr).toHex();
    
    f.close();
}


QByteArray AESCrypt::readBinary(QString filePath)
{
    QFile f(filePath);    
    if(!f.open(QIODevice::ReadOnly)){
        qDebug()<<" Failed to Open to the file "+filePath+"__>"+f.errorString();
        return QByteArray();
    }
    //    QDataStream in(&f);
    //        in.setByteOrder(QDataStream::LittleEndian); // *** set little endian byte order
    QByteArray arr=f.readAll();
    //    in>>arr;
    
    f.close();
    qDebug()<<" J ai lu "+QString::number(arr.size())+" "+hash(arr).toHex();
    return arr;
}

QByteArray AESCrypt::encrypt(QByteArray data, QString _pass)
{
    qDebug()<<"pass to encrypt "+_pass;
    QByteArray chiperKey = hash(_pass.toLocal8Bit());
    key =  QCA::SymmetricKey(chiperKey.left(64));
    iv = QCA::InitializationVector(chiperKey.right(64));
    QCA::Cipher cipher(CODEC,QCA::Cipher::CBC,QCA::Cipher::DefaultPadding, QCA::Encode,key, iv);
    
    QList<QByteArray> lista = split(data, 15);
    
    QCA::SecureArray encrypted;
    foreach (QByteArray item, lista) {
        cipher.setup(QCA::Encode, key, iv);
        QCA::SecureArray secureData = cipher.update(item);
        QCA::SecureArray encryptedData = cipher.final();
        if (!cipher.ok()) {
            qDebug() << "Encryption failed !";
            return "";
        }
        encrypted.append(encryptedData);
    }
    return encrypted.toByteArray();
}

QByteArray AESCrypt::decrypt(QByteArray data, QString _pass)
{
    qDebug()<<"pass to decrypt "+_pass;
    QByteArray chiperKey = hash(_pass.toLocal8Bit());
    key =  QCA::SymmetricKey(chiperKey.left(64));
    iv = QCA::InitializationVector(chiperKey.right(64));
    QCA::Cipher cipher = QCA::Cipher(CODEC,QCA::Cipher::CBC,QCA::Cipher::DefaultPadding, QCA::Decode,key,iv);
    
    QList<QByteArray> lista = split(data, 16);
    QCA::SecureArray encrypted;
    foreach (QByteArray item, lista) {
        if(item.size()>0){
            cipher.setup(QCA::Decode, key, iv);
            QCA::SecureArray encryptedData = cipher.process(item);
            if (!cipher.ok()) {
                qDebug() << "Decryption failed !";
                return "";
            }
            encrypted.append(encryptedData);
        }
    }
    return QString(encrypted.data()).toUtf8();
}

Thank you