QtAES算法详解与应用实例

一、介绍

QtAES是一款基于Qt框架的AES（高级加密标准）算法的实现工具，在数据传输、保护隐私等方面有广泛的应用。该算法采用了先进的密码学设计，可实现128、192和256位的加解密操作，以及ECB、CBC、CFB和OFB等加密模式。

二、核心原理

1、加密原理

AES算法采用分组密码机制，对明文块进行逐块加密。具体而言，AES将每个明文块分成16个字节，然后在4 × 4的矩阵上进行操作。首先对矩阵进行一个初始的变换（AddRoundKey），然后进行9轮操作，每轮都包含四个步骤，分别是SubBytes、ShiftRows、MixColumns和AddRoundKey。最后一轮没有MixColumns步骤，加密结束后，将密文块链接起来。

void AES::EncryptBlock(unsigned char *Block)
{
    // ...
    for (int i = 0; i < Nb; i++, ptr += 4) {
        for (int n = 0; n < 4; n++) {
            State[n][i] = Block[ptr + n];
        }
    }
    // ...
    AddRoundKey(0);
    // ...
    for (int round = 1; round < Nr; ++round) {
        // ...
        SubBytes();
        ShiftRows();
        MixColumns();
        AddRoundKey(round);
        // ...
    }
    // ...
}

2、解密原理

解密与加密过程类似，只是多了一个逆向操作步骤。即先进行一个AddRoundKey，然后进行9轮的逆向操作，分别是InvSubBytes、InvShiftRows、InvMixColumns和AddRoundKey。最后一轮没有InvMixColumns，解密结束后，将明文块链接起来。

void AES::DecryptBlock(unsigned char *Block)
{
    // ...
    for (int i = 0; i < Nb; i++, ptr += 4) {
        for (int n = 0; n = 1; --round) {
        // ...
        InvShiftRows();
        InvSubBytes();
        AddRoundKey(round);
        InvMixColumns();
        // ...
    }
    // ...
}

三、安装与配置

1、安装

官方提供了源代码，用户只需要下载并编译就能得到QtAES算法的程序。

$ git clone https://github.com/Lupino/qtaes.git
$ cd qtaes/qtaes/
$ qmake qtaes.pro
$ make

2、配置

用户可以通过修改源码中的qtaes_global.h文件来配置算法加密方式，如打开debug模式、显示加密过程等。

#define QT_AES_DEBUG
#define QT_AES_NO_QT_NAMESPACE
#define QT_AES_NO_QT_DEBUG_STREAM
#define QT_AES_NO_MEMBER_TEMPLATE_FRIENDS

#define QT_AES_NO_DEBUG_HELPER
#define QT_AES_SEPARATE_QT_RESOURCE_CPP
#define QT_AES_DISABLE_DEPRECATED_BEFORE

四、应用实例

1、文件加密

下面是一个简单的文件加密程序，实现了对文件的加密和解密操作。

#include <QFile>
#include <QCoreApplication>
#include <QDebug>
#include <qtaes.h>

#define KEY "1234567890123456"

int main(int argc, char *argv[])
{
    QCoreApplication app(argc, argv);

    QString fileName = "myfile.txt";
    QFile file(fileName);
    if (!file.open(QIODevice::ReadOnly)) {
        qDebug() << "Failed to open file " << fileName;
        return -1;
    }

    QByteArray data = file.readAll();
    file.close();

    QByteArray key16 = QByteArray(KEY).leftJustified(16);
    QByteArray iv = QByteArray(16, 0);
    QByteArray cipher = QtAES::encrypt(data, key16, iv, QtAES::AES_128, QtAES::CBC);
    qDebug() << "Cipher: " << QString(cipher.toHex());

    QByteArray plain = QtAES::decrypt(cipher, key16, iv, QtAES::AES_128, QtAES::CBC);
    qDebug() << "Plain: " << plain;

    return 0;
}

2、字符串加密

下面是一个将用户输入字符串加密的程序，用户可选择加密位数及模式。

#include <QCoreApplication>
#include <QDebug>
#include <qtaes.h>

int main(int argc, char *argv[])
{
    QCoreApplication app(argc, argv);

    QString text = "Hello World!";
    QByteArray data(text.toUtf8());

    QByteArray key16 = QByteArray("1234567890123456").leftJustified(16);
    QByteArray iv = QByteArray(16, 0);

    QByteArray cipher = QtAES::encrypt(data, key16, iv, QtAES::AES_128, QtAES::CBC);
    qDebug() << "Cipher: " << QString(cipher.toHex());

    QByteArray plain = QtAES::decrypt(cipher, key16, iv, QtAES::AES_128, QtAES::CBC);
    qDebug() << "Plain: " << plain;

    return 0;
}

3、网络传输加密

下面是一个使用Qt网络模块实现的加密网络传输程序，服务端将用户输入的字符串进行加密后通过TCP发送给客户端。

服务端：

#include <QObject>
#include <QStringList>
#include <QTcpServer>
#include <QTcpSocket>
#include <qtaes.h>

class Server : public QObject
{
    Q_OBJECT

public:
    explicit Server(QObject *parent = 0)
        : QObject(parent), mServer(new QTcpServer(this))
    {
        connect(mServer, &QTcpServer::newConnection, this, &Server::onNewConnection);
        if (!mServer->listen(QHostAddress::Any, 10000)) {
            qCritical() << mServer->errorString();
            return;
        } else {
            qDebug() << "Server started...";
        }
    }

private slots:
    void onNewConnection()
    {
        QTcpSocket *socket = mServer->nextPendingConnection();
        connect(socket, &QTcpSocket::disconnected, socket, &QTcpSocket::deleteLater);
        connect(socket, &QTcpSocket::readyRead, this, &Server::onReadyRead);
    }

    void onReadyRead()
    {
        QByteArray data = qobject_cast<QTcpSocket*>(sender())->readAll();
        QByteArray key16 = QByteArray("1234567890123456").leftJustified(16);
        QByteArray iv = QByteArray(16, 0);
        QByteArray cipher = QtAES::encrypt(data, key16, iv, QtAES::AES_128, QtAES::CBC);

        qDebug() << "Cipher: " << QString(cipher.toHex());
        qobject_cast<QTcpSocket*>(sender())->write(cipher);
    }

private:
    QTcpServer *mServer;
};

int main(int argc, char *argv[])
{
    QCoreApplication app(argc, argv);

    Server server;

    return app.exec();
}

客户端：

#include <QCoreApplication>
#include <QTcpSocket>
#include <QDebug>
#include <qtaes.h>

int main(int argc, char *argv[])
{
    QCoreApplication app(argc, argv);

    QTcpSocket socket;
    socket.connectToHost("127.0.0.1", 10000);
    if (!socket.waitForConnected()) {
        qDebug() << socket.errorString();
        return -1;
    }

    QString text = "Hello World!";
    QByteArray data(text.toUtf8());

    // Encrypt data
    QByteArray key16 = QByteArray("1234567890123456").leftJustified(16);
    QByteArray iv = QByteArray(16, 0);
    QByteArray cipher = QtAES::encrypt(data, key16, iv, QtAES::AES_128, QtAES::CBC);

    qDebug() << "Cipher: " << QString(cipher.toHex());
    // Send encrypted data
    qint64 bytesWritten = socket.write(cipher);
    qDebug() << "Bytes written: " << bytesWritten;
    socket.waitForBytesWritten();

    // Read encrypted data from server
    QByteArray buffer;
    while (socket.waitForReadyRead()) {
        buffer.append(socket.readAll());
    }

    qDebug() << "Received: " << buffer;
    // Decrypt data
    QByteArray plain = QtAES::decrypt(buffer, key16, iv, QtAES::AES_128, QtAES::CBC);

    qDebug() << "Plain: " << plain;

    return 0;
}