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)：

1 void encrypt(unsigned long *v, unsigned long *k) {
2     unsigned long y=v[0], z=v[1], sum=0, i;         /* set up */
3     unsigned long delta=0x9e3779b9;                 /* a key schedule constant */
4     unsigned long a=k[0], b=k[1], c=k[2], d=k[3];   /* cache key */
5     for (i=0; i < 32; i++) {                        /* basic cycle start */
6         sum += delta;
7         y += ((z<<4) + a) ^ (z + sum) ^ ((z>>5) + b);
8         z += ((y<<4) + c) ^ (y + sum) ^ ((y>>5) + d);/* end cycle */
9     }
10     v[0]=y;
11     v[1]=z;
12 }
13
14 void decrypt(unsigned long *v, unsigned long *k) {
15     unsigned long y=v[0], z=v[1], sum=0xC6EF3720, i; /* set up */
16     unsigned long delta=0x9e3779b9;                  /* a key schedule constant */
17     unsigned long a=k[0], b=k[1], c=k[2], d=k[3];    /* cache key */
18     for(i=0; i<32; i++) {                            /* basic cycle start */
19         z -= ((y<<4) + c) ^ (y + sum) ^ ((y>>5) + d);
20         y -= ((z<<4) + a) ^ (z + sum) ^ ((z>>5) + b);
21         sum -= delta;                                /* end cycle */
22     }
23     v[0]=y;
24     v[1]=z;
25 }

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

1 #ifndef UTIL_H
2 #define UTIL_H
3
4 #include <string>
5 #include <cstdlib>
6
7 typedef unsigned char byte;
8 typedef unsigned long ulong;
9
10 /*
11 *convert int to hex char.
12 *example:10 -> 'A',15 -> 'F'
13 */
14 char intToHexChar(int x);
15
16 /*
17 *convert hex char to int.
18 *example:'A' -> 10,'F' -> 15
19 */
20 int hexCharToInt(char hex);
21
22 using std::string;
23 /*
24 *convert a byte array to hex string.
25 *hex string format example:"AF B0 80 7D"
26 */
27 string bytesToHexString(const byte *in, size_t size);
28
29 /*
30 *convert a hex string to a byte array.
31 *hex string format example:"AF B0 80 7D"
32 */
33 size_t hexStringToBytes(const string &str, byte *out);
34
35 #endif/*UTIL_H*/

util.cpp

1 #include "util.h"
2 #include <vector>
3
4 using namespace std;
5
6 char intToHexChar(int x) {
7     static const char HEX[16] = {
8         '0', '1', '2', '3',
9         '4', '5', '6', '7',
10         '8', '9', 'A', 'B',
11         'C', 'D', 'E', 'F'
12     };
13     return HEX[x];
14 }
15
16 int hexCharToInt(char hex) {
17     hex = toupper(hex);
18     if (isdigit(hex))
19         return (hex - '0');
20     if (isalpha(hex))
21         return (hex - 'A' + 10);
22     return 0;
23 }
24
25 string bytesToHexString(const byte *in, size_t size) {
26     string str;
27     for (size_t i = 0; i < size; ++i) {
28         int t = in[i];
29         int a = t / 16;
30         int b = t % 16;
31         str.append(1, intToHexChar(a));
32         str.append(1, intToHexChar(b));
33         if (i != size - 1)
34             str.append(1, ' ');
35     }
36     return str;
37 }
38
39 size_t hexStringToBytes(const string &str, byte *out) {
40
41     vector<string> vec;
42     string::size_type currPos = 0, prevPos = 0;
43     while ((currPos = str.find(' ', prevPos)) != string::npos) {
44         string b(str.substr(prevPos, currPos - prevPos));
45         vec.push_back(b);
46         prevPos = currPos + 1;
47     }
48     if (prevPos < str.size()) {
49         string b(str.substr(prevPos));
50         vec.push_back(b);
51     }
52     typedef vector<string>::size_type sz_type;
53     sz_type size = vec.size();
54     for (sz_type i = 0; i < size; ++i) {
55         int a = hexCharToInt(vec[i][0]);
56         int b = hexCharToInt(vec[i][1]);
57         out[i] = a * 16 + b;
58     }
59     return size;
60 }

tea.h

1 #ifndef TEA_H
2 #define TEA_H
3
4 /*
5 *for htonl,htonl
6 *do remember link "ws2_32.lib"
7 */
8 #include <winsock2.h>
9 #include "util.h"
10
11 class TEA {
12 public:
13     TEA(const byte *key, int round = 32, bool isNetByte = false);
14     TEA(const TEA &rhs);
15     TEA& operator=(const TEA &rhs);
16     void encrypt(const byte *in, byte *out);
17     void decrypt(const byte *in, byte *out);
18 private:
19     void encrypt(const ulong *in, ulong *out);
20     void decrypt(const ulong *in, ulong *out);
21     ulong ntoh(ulong netlong) { return _isNetByte ? ntohl(netlong) : netlong; }
22     ulong hton(ulong hostlong) { return _isNetByte ? htonl(hostlong) : hostlong; }
23 private:
24     int _round; //iteration round to encrypt or decrypt
25     bool _isNetByte; //whether input bytes come from network
26     byte _key[16]; //encrypt or decrypt key
27 };
28
29 #endif/*TEA_H*/

tea.cpp

1 #include "tea.h"
2 #include <cstring> //for memcpy,memset
3
4 using namespace std;
5
6 TEA::TEA(const byte *key, int round /*= 32*/, bool isNetByte /*= false*/)
7 :_round(round)
8 ,_isNetByte(isNetByte) {
9     if (key != 0)
10         memcpy(_key, key, 16);
11     else
12         memset(_key, 0, 16);
13 }
14
15 TEA::TEA(const TEA &rhs)
16 :_round(rhs._round)
17 ,_isNetByte(rhs._isNetByte) {
18     memcpy(_key, rhs._key, 16);
19 }
20
21 TEA& TEA::operator=(const TEA &rhs) {
22     if (&rhs != this) {
23         _round = rhs._round;
24         _isNetByte = rhs._isNetByte;
25         memcpy(_key, rhs._key, 16);
26     }
27     return *this;
28 }
29
30 void TEA::encrypt(const byte *in, byte *out) {
31     encrypt((const ulong*)in, (ulong*)out);
32 }
33
34 void TEA::decrypt(const byte *in, byte *out) {
35     decrypt((const ulong*)in, (ulong*)out);
36 }
37
38 void TEA::encrypt(const ulong *in, ulong *out) {
39
40     ulong *k = (ulong*)_key;
41     register ulong y = ntoh(in[0]);
42     register ulong z = ntoh(in[1]);
43     register ulong a = ntoh(k[0]);
44     register ulong b = ntoh(k[1]);
45     register ulong c = ntoh(k[2]);
46     register ulong d = ntoh(k[3]);
47     register ulong delta = 0x9E3779B9; /* (sqrt(5)-1)/2*2^32 */
48     register int round = _round;
49     register ulong sum = 0;
50
51     while (round--) {    /* basic cycle start */
52         sum += delta;
53         y += ((z << 4) + a) ^ (z + sum) ^ ((z >> 5) + b);
54         z += ((y << 4) + c) ^ (y + sum) ^ ((y >> 5) + d);
55     }    /* end cycle */
56     out[0] = ntoh(y);
57     out[1] = ntoh(z);
58 }
59
60 void TEA::decrypt(const ulong *in, ulong *out) {
61
62     ulong *k = (ulong*)_key;
63     register ulong y = ntoh(in[0]);
64     register ulong z = ntoh(in[1]);
65     register ulong a = ntoh(k[0]);
66     register ulong b = ntoh(k[1]);
67     register ulong c = ntoh(k[2]);
68     register ulong d = ntoh(k[3]);
69     register ulong delta = 0x9E3779B9; /* (sqrt(5)-1)/2*2^32 */
70     register int round = _round;
71     register ulong sum = 0;
72
73     if (round == 32)
74         sum = 0xC6EF3720; /* delta << 5*/
75     else if (round == 16)
76         sum = 0xE3779B90; /* delta << 4*/
77     else
78         sum = delta * round;
79
80     while (round--) {    /* basic cycle start */
81         z -= ((y << 4) + c) ^ (y + sum) ^ ((y >> 5) + d);
82         y -= ((z << 4) + a) ^ (z + sum) ^ ((z >> 5) + b);
83         sum -= delta;
84     }    /* end cycle */
85     out[0] = ntoh(y);
86     out[1] = ntoh(z);
87 }

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

1 #include "tea.h"
2 #include "util.h"
3 #include <iostream>
4
5 using namespace std;
6
7 int main() {
8
9     const string plainStr("AD DE E2 DB B3 E2 DB B3");
10     const string keyStr("3A DA 75 21 DB E2 DB B3 11 B4 49 01 A5 C6 EA D4");
11     const int SIZE_IN = 8, SIZE_OUT = 8, SIZE_KEY = 16;
12     byte plain[SIZE_IN], crypt[SIZE_OUT], key[SIZE_KEY];
13
14     size_t size_in = hexStringToBytes(plainStr, plain);
15     size_t size_key = hexStringToBytes(keyStr, key);
16
17     if (size_in != SIZE_IN || size_key != SIZE_KEY)
18         return -1;
19
20     cout << "Plain: " << bytesToHexString(plain, size_in) << endl;
21     cout << "Key  : " << bytesToHexString(key, size_key) << endl;
22
23     TEA tea(key, 16, true);
24     tea.encrypt(plain, crypt);
25     cout << "Crypt: " << bytesToHexString(crypt, SIZE_OUT) << endl;
26
27     tea.decrypt(crypt, plain);
28     cout << "Plain: " << bytesToHexString(plain, SIZE_IN) << endl;
29     return 0;
30 }

运行结果：
Plain: AD DE E2 DB B3 E2 DB B3
Key  : 3A DA 75 21 DB E2 DB B3 11 B4 49 01 A5 C6 EA D4
Crypt: 3B 3B 4D 8C 24 3A FD F2
Plain: AD DE E2 DB B3 E2 DB B3