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