TEA加密算法的C/C++实现

TEA(Tiny Encryption Algorithm) 是一种简单高效的加密算法，以加密解密速度快，实现简单著称。算法真的很简单，TEA算法每一次可以操作64-bit(8-byte)，采用128-bit(16-byte)作为key，算法采用迭代的形式，推荐的迭代轮数是64轮，最少32轮。目前我只知道QQ一直用的是16轮TEA。没什么好说的，先给出C语言的源代码(默认是32轮)：

void encrypt(unsigned long *v, unsigned long *k) {
    unsigned ], z=v[], sum=, i;         /* set up */
    unsigned long delta=0x9e3779b9;                 /* a key schedule constant */
    unsigned ], b=k[], c=k[], d=k[];   /* cache key */
    ; i < ; i++) {                        /* basic cycle start */
        sum += delta;
        y += ((z<<) + a) ^ (z + sum) ^ ((z>>) + b);
        z += ((y<<) + c) ^ (y + sum) ^ ((y>>) + d);/* end cycle */
    }
    v[]=y;
    v[]=z;
}

void decrypt(unsigned long *v, unsigned long *k) {
    unsigned ], z=v[], sum=0xC6EF3720, i; /* set up */
    unsigned long delta=0x9e3779b9;                  /* a key schedule constant */
    unsigned ], b=k[], c=k[], d=k[];    /* cache key */
    ; i<; i++) {                            /* basic cycle start */
        z -= ((y<<) + c) ^ (y + sum) ^ ((y>>) + d);
        y -= ((z<<) + a) ^ (z + sum) ^ ((z>>) + b);
        sum -= delta;                                /* end cycle */
    }
    v[]=y;
    v[]=z;
}

C语言写的用起来当然不方便，没关系，用C++封装以下就OK了：

util.h

#ifndef UTIL_H
#define UTIL_H

#include <string>
#include <cstdlib>

typedef unsigned char byte;
typedef unsigned long ulong;

/*
*convert int to hex char.
*example:10 -> 'A',15 -> 'F'
*/
char intToHexChar(int x);

/*
*convert hex char to int.
*example:'A' -> 10,'F' -> 15
*/
int hexCharToInt(char hex);

using std::string;
/*
*convert a byte array to hex string.
*hex string format example:"AF B0 80 7D"
*/
string bytesToHexString(const byte *in, size_t size);

/*
*convert a hex string to a byte array.
*hex string format example:"AF B0 80 7D"
*/
size_t hexStringToBytes(const string &str, byte *out);

#endif/*UTIL_H*/

util.cpp

#include "util.h"
#include <vector>

using namespace std;

char intToHexChar(int x) {
    ] = {
        ',
        ',
        ', 'A', 'B',
        'C', 'D', 'E', 'F'
    };
    return HEX[x];
}

int hexCharToInt(char hex) {
    hex = toupper(hex);
    if (isdigit(hex))
        ');
    if (isalpha(hex))
        );
    ;
}

string bytesToHexString(const byte *in, size_t size) {
    string str;
    ; i < size; ++i) {
        int t = in[i];
        ;
        ;
        str.append(, intToHexChar(a));
        str.append(, intToHexChar(b));
        )
            str.append(, ' ');
    }
    return str;
}

size_t hexStringToBytes(const string &str, byte *out) {

    vector<string> vec;
    , prevPos = ;
    while ((currPos = str.find(' ', prevPos)) != string::npos) {
        string b(str.substr(prevPos, currPos - prevPos));
        vec.push_back(b);
        prevPos = currPos + ;
    }
    if (prevPos < str.size()) {
        string b(str.substr(prevPos));
        vec.push_back(b);
    }
    typedef vector<string>::size_type sz_type;
    sz_type size = vec.size();
    ; i < size; ++i) {
        ]);
        ]);
         + b;
    }
    return size;
}

tea.h

#ifndef TEA_H
#define TEA_H

/*
*for htonl,htonl
*do remember link "ws2_32.lib"
*/
#include <winsock2.h>
#include "util.h"

class TEA {
public:
    TEA(, bool isNetByte = false);
    TEA(const TEA &rhs);
    TEA& operator=(const TEA &rhs);
    void encrypt(const byte *in, byte *out);
    void decrypt(const byte *in, byte *out);
private:
    void encrypt(const ulong *in, ulong *out);
    void decrypt(const ulong *in, ulong *out);
    ulong ntoh(ulong netlong) { return _isNetByte ? ntohl(netlong) : netlong; }
    ulong hton(ulong hostlong) { return _isNetByte ? htonl(hostlong) : hostlong; }
private:
    int _round; //iteration round to encrypt or decrypt
    bool _isNetByte; //whether input bytes come from network
    ]; //encrypt or decrypt key
};

#endif/*TEA_H*/

tea.cpp

#include "tea.h"
#include <cstring> //for memcpy,memset

using namespace std;

TEA::TEA(const byte *key, int round /*= 32*/, bool isNetByte /*= false*/)
:_round(round)
,_isNetByte(isNetByte) {
    )
        memcpy(_key, key, );
    else
        memset(_key, , );
}

TEA::TEA(const TEA &rhs)
:_round(rhs._round)
,_isNetByte(rhs._isNetByte) {
    memcpy(_key, rhs._key, );
}

TEA& TEA::operator=(const TEA &rhs) {
    if (&rhs != this) {
        _round = rhs._round;
        _isNetByte = rhs._isNetByte;
        memcpy(_key, rhs._key, );
    }
    return *this;
}

void TEA::encrypt(const byte *in, byte *out) {
    encrypt((const ulong*)in, (ulong*)out);
}

void TEA::decrypt(const byte *in, byte *out) {
    decrypt((const ulong*)in, (ulong*)out);
}

void TEA::encrypt(const ulong *in, ulong *out) {

    ulong *k = (ulong*)_key;
    register ]);
    register ]);
    register ]);
    register ]);
    register ]);
    register ]);
    register ulong delta = 0x9E3779B9; /* (sqrt(5)-1)/2*2^32 */
    register int round = _round;
    register ;

    while (round--) {    /* basic cycle start */
        sum += delta;
        y += ((z << ) + a) ^ (z + sum) ^ ((z >> ) + b);
        z += ((y << ) + c) ^ (y + sum) ^ ((y >> ) + d);
    }    /* end cycle */
    ] = ntoh(y);
    ] = ntoh(z);
}

void TEA::decrypt(const ulong *in, ulong *out) {

    ulong *k = (ulong*)_key;
    register ]);
    register ]);
    register ]);
    register ]);
    register ]);
    register ]);
    register ulong delta = 0x9E3779B9; /* (sqrt(5)-1)/2*2^32 */
    register int round = _round;
    register ;

    )
        sum = 0xC6EF3720; /* delta << 5*/
    )
        sum = 0xE3779B90; /* delta << 4*/
    else
        sum = delta * round;

    while (round--) {    /* basic cycle start */
        z -= ((y << ) + c) ^ (y + sum) ^ ((y >> ) + d);
        y -= ((z << ) + a) ^ (z + sum) ^ ((z >> ) + b);
        sum -= delta;
    }    /* end cycle */
    ] = ntoh(y);
    ] = ntoh(z);
}

需要说明的是TEA的构造函数：
TEA(const byte *key, int round = 32, bool isNetByte = false);
1.key - 加密或解密用的128-bit(16byte)密钥。
2.round - 加密或解密的轮数，常用的有64，32，16。
3.isNetByte - 用来标记待处理的字节是不是来自网络，为true时在加密/解密前先要转换成本地字节，执行加密/解密，然后再转换回网络字节。偷偷告诉你，QQ就是这样做的！

最后当然少不了测试代码：
test.cpp

#include "tea.h"
#include "util.h"
#include <iostream>

using namespace std;

int main() {

    const string plainStr("AD DE E2 DB B3 E2 DB B3");
    const string keyStr("3A DA 75 21 DB E2 DB B3 11 B4 49 01 A5 C6 EA D4");
    , SIZE_OUT = , SIZE_KEY = ;
    byte plain[SIZE_IN], crypt[SIZE_OUT], key[SIZE_KEY];

    size_t size_in = hexStringToBytes(plainStr, plain);
    size_t size_key = hexStringToBytes(keyStr, key);

    if (size_in != SIZE_IN || size_key != SIZE_KEY)
        ;

    cout << "Plain: " << bytesToHexString(plain, size_in) << endl;
    cout << "Key  : " << bytesToHexString(key, size_key) << endl;

    TEA tea(key, , true);
    tea.encrypt(plain, crypt);
    cout << "Crypt: " << bytesToHexString(crypt, SIZE_OUT) << endl;

    tea.decrypt(crypt, plain);
    cout << "Plain: " << bytesToHexString(plain, SIZE_IN) << endl;
    ;
}

运行结果：

Plain: AD DE E2 DB B3 E2 DB B3
Key  : 3A DA   DB E2 DB B3  B4   A5 C6 EA D4
Crypt: 3B 3B 4D 8C  3A FD F2
Plain: AD DE E2 DB B3 E2 DB B3