tea.cpp

tea 加密算法 qq使用的就是这个加密算法来 解决登陆问题

#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) 
{
    if (key != 0)
        memcpy(_key, key, 16);
    else
        memset(_key, 0, 16);
}

TEA::TEA(const TEA &rhs):_round(rhs._round),_isNetByte(rhs._isNetByte) {    
	memcpy(_key, rhs._key, 16);
}

TEA& TEA::operator=(const TEA &rhs) {
    if (&rhs != this) {
        _round = rhs._round;
        _isNetByte = rhs._isNetByte;
        memcpy(_key, rhs._key, 16);
    }
    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 ulong y = ntoh(in[0]);
    register ulong z = ntoh(in[1]);
    register ulong a = ntoh(k[0]);
    register ulong b = ntoh(k[1]);
    register ulong c = ntoh(k[2]);
    register ulong d = ntoh(k[3]);
    register ulong delta = 0x9E3779B9; /* (sqrt(5)-1)/2*2^32 */
    register int round = _round;
    register ulong sum = 0;

    while (round--) {    /* basic cycle start */
        sum += delta;
        y += ((z << 4) + a) ^ (z + sum) ^ ((z >> 5) + b);
        z += ((y << 4) + c) ^ (y + sum) ^ ((y >> 5) + d);
    }    /* end cycle */
    out[0] = ntoh(y);
    out[1] = ntoh(z);
}

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

    ulong *k = (ulong*)_key;
    register ulong y = ntoh(in[0]);
    register ulong z = ntoh(in[1]);
    register ulong a = ntoh(k[0]);
    register ulong b = ntoh(k[1]);
    register ulong c = ntoh(k[2]);
    register ulong d = ntoh(k[3]);
    register ulong delta = 0x9E3779B9; /* (sqrt(5)-1)/2*2^32 */
    register int round = _round;
    register ulong sum = 0;

    if (round == 32)
        sum = 0xC6EF3720; /* delta << 5*/
    else if (round == 16)
        sum = 0xE3779B90; /* delta << 4*/
    else
        sum = delta << static_cast<int>(logbase(2, round));

    while (round--) {    /* basic cycle start */
        z -= ((y << 4) + c) ^ (y + sum) ^ ((y >> 5) + d);
        y -= ((z << 4) + a) ^ (z + sum) ^ ((z >> 5) + b);
        sum -= delta;
    }    /* end cycle */
    out[0] = ntoh(y);
    out[1] = ntoh(z);
}