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
5 #include
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
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
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
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
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)/2232 /
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)/22^32 /
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
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
文章转载自：http://www.cppblog.com/ant/archive/2007/10/12/31326.html
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