AES加密算法C++实现

　　我从网上下载了一套AES加密算法的C++实现，代码如下：

（1）aes.h

#ifndef SRC_UTILS_AES_H
#define SRC_UTILS_AES_H

class AES  
{
public:
    AES(unsigned char* key);
    virtual ~AES();
    unsigned char* Cipher(unsigned char* input);　　　　// 加密，传入的数组大小必须是16字节
    unsigned char* InvCipher(unsigned char* input);　　// 解密，传入的数组也必须是16字节
    void* Cipher(void* input, int length=0);　　　　　　// 可以传入数组，大小必须是16的整数倍，如果不是将会越界操作；如果不传length而默认为0，那么将按照字符串处理，遇'\0'结束
    void* InvCipher(void* input, int length);　　　　　 // 必须传入数组和大小，必须是16的整数倍

private:
    unsigned char Sbox[256];
    unsigned char InvSbox[256];
    unsigned char w[11][4][4];

    void KeyExpansion(unsigned char* key, unsigned char w[][4][4]);
    unsigned char FFmul(unsigned char a, unsigned char b);

    void SubBytes(unsigned char state[][4]);
    void ShiftRows(unsigned char state[][4]);
    void MixColumns(unsigned char state[][4]);
    void AddRoundKey(unsigned char state[][4], unsigned char k[][4]);

    void InvSubBytes(unsigned char state[][4]);
    void InvShiftRows(unsigned char state[][4]);
    void InvMixColumns(unsigned char state[][4]);
};

#endif    // SRC_UTILS_AES_H

（2）aes.cpp

#include "aes.h"
#include "string.h"

AES::AES(unsigned char* key)
{
    unsigned char sBox[] =
    { /*  0    1    2    3    4    5    6    7    8    9    a    b    c    d    e    f */ 
        0x63,0x7c,0x77,0x7b,0xf2,0x6b,0x6f,0xc5,0x30,0x01,0x67,0x2b,0xfe,0xd7,0xab,0x76, /*0*/  
        0xca,0x82,0xc9,0x7d,0xfa,0x59,0x47,0xf0,0xad,0xd4,0xa2,0xaf,0x9c,0xa4,0x72,0xc0, /*1*/
        0xb7,0xfd,0x93,0x26,0x36,0x3f,0xf7,0xcc,0x34,0xa5,0xe5,0xf1,0x71,0xd8,0x31,0x15, /*2*/ 
        0x04,0xc7,0x23,0xc3,0x18,0x96,0x05,0x9a,0x07,0x12,0x80,0xe2,0xeb,0x27,0xb2,0x75, /*3*/ 
        0x09,0x83,0x2c,0x1a,0x1b,0x6e,0x5a,0xa0,0x52,0x3b,0xd6,0xb3,0x29,0xe3,0x2f,0x84, /*4*/ 
        0x53,0xd1,0x00,0xed,0x20,0xfc,0xb1,0x5b,0x6a,0xcb,0xbe,0x39,0x4a,0x4c,0x58,0xcf, /*5*/
        0xd0,0xef,0xaa,0xfb,0x43,0x4d,0x33,0x85,0x45,0xf9,0x02,0x7f,0x50,0x3c,0x9f,0xa8, /*6*/  
        0x51,0xa3,0x40,0x8f,0x92,0x9d,0x38,0xf5,0xbc,0xb6,0xda,0x21,0x10,0xff,0xf3,0xd2, /*7*/ 
        0xcd,0x0c,0x13,0xec,0x5f,0x97,0x44,0x17,0xc4,0xa7,0x7e,0x3d,0x64,0x5d,0x19,0x73, /*8*/ 
        0x60,0x81,0x4f,0xdc,0x22,0x2a,0x90,0x88,0x46,0xee,0xb8,0x14,0xde,0x5e,0x0b,0xdb, /*9*/ 
        0xe0,0x32,0x3a,0x0a,0x49,0x06,0x24,0x5c,0xc2,0xd3,0xac,0x62,0x91,0x95,0xe4,0x79, /*a*/
        0xe7,0xc8,0x37,0x6d,0x8d,0xd5,0x4e,0xa9,0x6c,0x56,0xf4,0xea,0x65,0x7a,0xae,0x08, /*b*/
        0xba,0x78,0x25,0x2e,0x1c,0xa6,0xb4,0xc6,0xe8,0xdd,0x74,0x1f,0x4b,0xbd,0x8b,0x8a, /*c*/ 
        0x70,0x3e,0xb5,0x66,0x48,0x03,0xf6,0x0e,0x61,0x35,0x57,0xb9,0x86,0xc1,0x1d,0x9e, /*d*/
        0xe1,0xf8,0x98,0x11,0x69,0xd9,0x8e,0x94,0x9b,0x1e,0x87,0xe9,0xce,0x55,0x28,0xdf, /*e*/ 
        0x8c,0xa1,0x89,0x0d,0xbf,0xe6,0x42,0x68,0x41,0x99,0x2d,0x0f,0xb0,0x54,0xbb,0x16  /*f*/
    };
    unsigned char invsBox[256] = 
    { /*  0    1    2    3    4    5    6    7    8    9    a    b    c    d    e    f  */  
        0x52,0x09,0x6a,0xd5,0x30,0x36,0xa5,0x38,0xbf,0x40,0xa3,0x9e,0x81,0xf3,0xd7,0xfb, /*0*/ 
        0x7c,0xe3,0x39,0x82,0x9b,0x2f,0xff,0x87,0x34,0x8e,0x43,0x44,0xc4,0xde,0xe9,0xcb, /*1*/
        0x54,0x7b,0x94,0x32,0xa6,0xc2,0x23,0x3d,0xee,0x4c,0x95,0x0b,0x42,0xfa,0xc3,0x4e, /*2*/ 
        0x08,0x2e,0xa1,0x66,0x28,0xd9,0x24,0xb2,0x76,0x5b,0xa2,0x49,0x6d,0x8b,0xd1,0x25, /*3*/ 
        0x72,0xf8,0xf6,0x64,0x86,0x68,0x98,0x16,0xd4,0xa4,0x5c,0xcc,0x5d,0x65,0xb6,0x92, /*4*/ 
        0x6c,0x70,0x48,0x50,0xfd,0xed,0xb9,0xda,0x5e,0x15,0x46,0x57,0xa7,0x8d,0x9d,0x84, /*5*/ 
        0x90,0xd8,0xab,0x00,0x8c,0xbc,0xd3,0x0a,0xf7,0xe4,0x58,0x05,0xb8,0xb3,0x45,0x06, /*6*/ 
        0xd0,0x2c,0x1e,0x8f,0xca,0x3f,0x0f,0x02,0xc1,0xaf,0xbd,0x03,0x01,0x13,0x8a,0x6b, /*7*/
        0x3a,0x91,0x11,0x41,0x4f,0x67,0xdc,0xea,0x97,0xf2,0xcf,0xce,0xf0,0xb4,0xe6,0x73, /*8*/ 
        0x96,0xac,0x74,0x22,0xe7,0xad,0x35,0x85,0xe2,0xf9,0x37,0xe8,0x1c,0x75,0xdf,0x6e, /*9*/
        0x47,0xf1,0x1a,0x71,0x1d,0x29,0xc5,0x89,0x6f,0xb7,0x62,0x0e,0xaa,0x18,0xbe,0x1b, /*a*/
        0xfc,0x56,0x3e,0x4b,0xc6,0xd2,0x79,0x20,0x9a,0xdb,0xc0,0xfe,0x78,0xcd,0x5a,0xf4, /*b*/ 
        0x1f,0xdd,0xa8,0x33,0x88,0x07,0xc7,0x31,0xb1,0x12,0x10,0x59,0x27,0x80,0xec,0x5f, /*c*/ 
        0x60,0x51,0x7f,0xa9,0x19,0xb5,0x4a,0x0d,0x2d,0xe5,0x7a,0x9f,0x93,0xc9,0x9c,0xef, /*d*/ 
        0xa0,0xe0,0x3b,0x4d,0xae,0x2a,0xf5,0xb0,0xc8,0xeb,0xbb,0x3c,0x83,0x53,0x99,0x61, /*e*/ 
        0x17,0x2b,0x04,0x7e,0xba,0x77,0xd6,0x26,0xe1,0x69,0x14,0x63,0x55,0x21,0x0c,0x7d  /*f*/
    }; 
    memcpy(Sbox, sBox, 256);
    memcpy(InvSbox, invsBox, 256);
    KeyExpansion(key, w);
}

AES::~AES()
{

}

unsigned char* AES::Cipher(unsigned char* input)
{
    unsigned char state[4][4];
    int i,r,c;

    for(r=0; r<4; r++)
    {
        for(c=0; c<4 ;c++)
        {
            state[r][c] = input[c*4+r];
        }
    }

    AddRoundKey(state,w[0]);

    for(i=1; i<=10; i++)
    {
        SubBytes(state);
        ShiftRows(state);
        if(i!=10)MixColumns(state);
        AddRoundKey(state,w[i]);
    }

    for(r=0; r<4; r++)
    {
        for(c=0; c<4 ;c++)
        {
            input[c*4+r] = state[r][c];
        }
    }

    return input;
}

unsigned char* AES::InvCipher(unsigned char* input)
{
    unsigned char state[4][4];
    int i,r,c;

    for(r=0; r<4; r++)
    {
        for(c=0; c<4 ;c++)
        {
            state[r][c] = input[c*4+r];
        }
    }

    AddRoundKey(state, w[10]);
    for(i=9; i>=0; i--)
    {
        InvShiftRows(state);
        InvSubBytes(state);
        AddRoundKey(state, w[i]);
        if(i)
        {
            InvMixColumns(state);
        }
    }
    
    for(r=0; r<4; r++)
    {
        for(c=0; c<4 ;c++)
        {
            input[c*4+r] = state[r][c];
        }
    }

    return input;
}

void* AES::Cipher(void* input, int length)
{
    unsigned char* in = (unsigned char*) input;
    int i;
    if(!length)        // 如果是0则当做字符串处理
    {
        while(*(in+length++));
        in = (unsigned char*) input;
    }
    for(i=0; i<length; i+=16)
    {
        Cipher(in+i);
    }
    return input;
}

void* AES::InvCipher(void* input, int length)
{
    unsigned char* in = (unsigned char*) input;
    int i;
    for(i=0; i<length; i+=16)
    {
        InvCipher(in+i);
    }
    return input;
}

void AES::KeyExpansion(unsigned char* key, unsigned char w[][4][4])
{
    int i,j,r,c;
    unsigned char rc[] = {0x01, 0x02, 0x04, 0x08, 0x10, 0x20, 0x40, 0x80, 0x1b, 0x36};
    for(r=0; r<4; r++)
    {
        for(c=0; c<4; c++)
        {
            w[0][r][c] = key[r+c*4];
        }
    }
    for(i=1; i<=10; i++)
    {
        for(j=0; j<4; j++)
        {
            unsigned char t[4];
            for(r=0; r<4; r++)
            {
                t[r] = j ? w[i][r][j-1] : w[i-1][r][3];
            }
            if(j == 0)
            {
                unsigned char temp = t[0];
                for(r=0; r<3; r++)
                {
                    t[r] = Sbox[t[(r+1)%4]];
                }
                t[3] = Sbox[temp];
                t[0] ^= rc[i-1];
            }
            for(r=0; r<4; r++)
            {
                w[i][r][j] = w[i-1][r][j] ^ t[r];
            }
        }
    }
}

unsigned char AES::FFmul(unsigned char a, unsigned char b)
{
    unsigned char bw[4];
    unsigned char res=0;
    int i;
    bw[0] = b;
    for(i=1; i<4; i++)
    {
        bw[i] = bw[i-1]<<1;
        if(bw[i-1]&0x80)
        {
            bw[i]^=0x1b;
        }
    }
    for(i=0; i<4; i++)
    {
        if((a>>i)&0x01)
        {
            res ^= bw[i];
        }
    }
    return res;
}

void AES::SubBytes(unsigned char state[][4])
{
    int r,c;
    for(r=0; r<4; r++)
    {
        for(c=0; c<4; c++)
        {
            state[r][c] = Sbox[state[r][c]];
        }
    }
}

void AES::ShiftRows(unsigned char state[][4])
{
    unsigned char t[4];
    int r,c;
    for(r=1; r<4; r++)
    {
        for(c=0; c<4; c++)
        {
            t[c] = state[r][(c+r)%4];
        }
        for(c=0; c<4; c++)
        {
            state[r][c] = t[c];
        }
    }
}

void AES::MixColumns(unsigned char state[][4])
{
    unsigned char t[4];
    int r,c;
    for(c=0; c< 4; c++)
    {
        for(r=0; r<4; r++)
        {
            t[r] = state[r][c];
        }
        for(r=0; r<4; r++)
        {
            state[r][c] = FFmul(0x02, t[r])
                        ^ FFmul(0x03, t[(r+1)%4])
                        ^ FFmul(0x01, t[(r+2)%4])
                        ^ FFmul(0x01, t[(r+3)%4]);
        }
    }
}

void AES::AddRoundKey(unsigned char state[][4], unsigned char k[][4])
{
    int r,c;
    for(c=0; c<4; c++)
    {
        for(r=0; r<4; r++)
        {
            state[r][c] ^= k[r][c];
        }
    }
}

void AES::InvSubBytes(unsigned char state[][4])
{
    int r,c;
    for(r=0; r<4; r++)
    {
        for(c=0; c<4; c++)
        {
            state[r][c] = InvSbox[state[r][c]];
        }
    }
}

void AES::InvShiftRows(unsigned char state[][4])
{
    unsigned char t[4];
    int r,c;
    for(r=1; r<4; r++)
    {
        for(c=0; c<4; c++)
        {
            t[c] = state[r][(c-r+4)%4];
        }
        for(c=0; c<4; c++)
        {
            state[r][c] = t[c];
        }
    }
}

void AES::InvMixColumns(unsigned char state[][4])
{
    unsigned char t[4];
    int r,c;
    for(c=0; c< 4; c++)
    {
        for(r=0; r<4; r++)
        {
            t[r] = state[r][c];
        }
        for(r=0; r<4; r++)
        {
            state[r][c] = FFmul(0x0e, t[r])
                        ^ FFmul(0x0b, t[(r+1)%4])
                        ^ FFmul(0x0d, t[(r+2)%4])
                        ^ FFmul(0x09, t[(r+3)%4]);
        }
    }
}

　　上面的加密算法是没问题的，但是接口有两个需要注意的地方，也就是在头文件中备注的地方：

1、数组的大小必须是16字节或者16的整数倍。

2、不能直接使用字符串输出，因为加密后的数组内容可能有'\0'，字符串会被截断。

　　为了更方便的使用此加密算法，我封装了一个接口类，声明如下：

（3）aes_encryptor.h

#ifndef SRC_UTILS_AES_ENCRYPTOR_H
#define SRC_UTILS_AES_ENCRYPTOR_H

#include <string>

class AES;

class AesEncryptor
{
public:
    AesEncryptor(unsigned char* key);
    ~AesEncryptor(void);

    std::string EncryptString(std::string strInfor);
    std::string DecryptString(std::string strMessage);

    void EncryptTxtFile(const char* inputFileName, const char* outputFileName);
    void DecryptTxtFile(const char* inputFileName, const char* outputFileName);

private:
    void Byte2Hex(const unsigned char* src, int len, char* dest);
    void Hex2Byte(const char* src, int len, unsigned char* dest);
    int  Char2Int(char c);

private:
    AES* m_pEncryptor;
};

#endif        // SRC_UTILS_AES_ENCRYPTOR_H

 （4）aes_encryptor.cpp

#include "aes.h"
#include "aes_encryptor.h"
#include "log.h"

#include <fstream>
using namespace std;

AesEncryptor::AesEncryptor(unsigned char* key)
{
    m_pEncryptor = new AES(key);
}


AesEncryptor::~AesEncryptor(void)
{
    delete m_pEncryptor;
}

void AesEncryptor::Byte2Hex(const unsigned char* src, int len, char* dest) {
    for (int i=0; i<len; ++i) {
        sprintf_s(dest + i * 2, 3, "%02X", src[i]);    
    }
}

void AesEncryptor::Hex2Byte(const char* src, int len, unsigned char* dest) {
    int length = len / 2;
    for (int i=0; i<length; ++i) {
        dest[i] = Char2Int(src[i * 2]) * 16 + Char2Int(src[i * 2 + 1]);
    }
}

int AesEncryptor::Char2Int(char c) {
    if ('0' <= c && c <= '9') {
        return (c - '0');
    }
    else if ('a' <= c && c<= 'f') {
        return (c - 'a' + 10);
    }
    else if ('A' <= c && c<= 'F') {
        return (c - 'A' + 10);
    }
    return -1;
}

string AesEncryptor::EncryptString(string strInfor) {
    int nLength = strInfor.length();
    int spaceLength = 16 - (nLength % 16);
    unsigned char* pBuffer = new unsigned char[nLength + spaceLength];
    memset(pBuffer, '\0', nLength + spaceLength);
    memcpy_s(pBuffer, nLength + spaceLength, strInfor.c_str(), nLength);
    m_pEncryptor->Cipher(pBuffer, nLength + spaceLength);
    
    // 这里需要把得到的字符数组转换成十六进制字符串 
    char* pOut = new char[2 * (nLength + spaceLength)];
    memset(pOut, '\0', 2 * (nLength + spaceLength));
    Byte2Hex(pBuffer, nLength + spaceLength, pOut);

    string retValue(pOut);
    delete[] pBuffer;
    delete[] pOut;
    return retValue;
}

string AesEncryptor::DecryptString(string strMessage) {
    int nLength = strMessage.length() / 2;
    unsigned char* pBuffer = new unsigned char[nLength];
    memset(pBuffer, '\0', nLength);
    Hex2Byte(strMessage.c_str(), strMessage.length(), pBuffer);

    m_pEncryptor->InvCipher(pBuffer, nLength);
    string retValue((char*)pBuffer);
    delete[] pBuffer;
    return retValue;
}

void AesEncryptor::EncryptTxtFile(const char* inputFileName, const char* outputFileName) {
    ifstream ifs;

    // Open file:
    ifs.open(inputFileName);
    if (!ifs) {
        UNILOGW("AesEncryptor::EncryptTxtFile() - Open input file failed!");
        return ;
    }

    // Read config data:
    string strInfor;
    string strLine;
    while (!ifs.eof()) {
        char temp[1024];
        memset(temp, '\0', 1024);
        ifs.read(temp, 1000);
        strInfor += temp;
    }
    ifs.close();

    // Encrypt
    strLine = EncryptString(strInfor);

    // Writefile 
    ofstream ofs;
    ofs.open(outputFileName);
    if (!ofs) {
        UNILOGW("AesEncryptor::EncryptTxtFile() - Open output file failed!");
        return ;
    }
    ofs << strLine;
    ofs.close();
}

void AesEncryptor::DecryptTxtFile(const char* inputFile, const char* outputFile) {
    ifstream ifs;

    // Open file:
    ifs.open(inputFile);
    if (!ifs) {
        UNILOGW("AesEncryptor::DecryptTxtFile() - Open input file failed!");
        return ;
    }

    // Read config data:
    string strInfor;
    string strLine;
    while (!ifs.eof()) {
        char temp[1024];
        memset(temp, '\0', 1024);
        ifs.read(temp, 1000);
        strInfor += temp;
    }
    ifs.close();

    // Encrypt
    strLine = DecryptString(strInfor);

    // Writefile 
    ofstream ofs;
    ofs.open(outputFile);
    if (!ofs) {
        UNILOGW("AesEncryptor::DecryptTxtFile() - Open output file failed!");
        return ;
    }
    ofs << strLine;
    ofs.close();
}

　　从代码中可以看到增加了以下特性：

1、支持对std::string 字符串类型的加密，并返回相应的字符串，这个字符串是将加密后的内容转换成十六进制表示的，所以不存在截断的问题。当然了，解密的时候也需要转换成真正的unsigned char数组；

2、支持直接对文本文件进行加密，指定输入和输出的文件名即可。

PS: 多说一句，从网上看别人封装的代码时，先看评论和反应，有的时候网友写个带漏洞的程序坑死人不负责的。