装配代码。加密解密例程

Question

• 有人能帮我看看这个，帮我找出一个解密来逆转用户输入的字符串吗？我不是说只是做这个程序的反面。推送edx不eax添加eax,0x04 mov edx，eax pop eax xor eax，edx pop rol al,1 rol al,1 sub，0x02 ret *

寄存器是:内- ecx:加密密钥.要加密的字符。

向外- eax:加密字符

谢谢你花时间看我。

Answer 1

该算法是对称的，因为我可以解密每个字符和密钥组合。

循环测试了这两个函数在解密返回值时是否有任何错误：

#include <iostream>
using namespace std;

unsigned char enc(unsigned char ch, unsigned char key)
{
    unsigned char tmp = key^(~ch+(unsigned char)0x04);
    return (( (tmp<<3) | (tmp>>5) ) & 0xff)-0x02;
}

unsigned char dec(unsigned char ch, unsigned char key)
{
    unsigned char tmp = (ch+0x02);
    tmp = ((tmp>>3) | (tmp<<5)) & 0xff;
    return ~((tmp^key )-(unsigned char)0x04);
}

int main()
{
    // single encryption test
    char c = 'A';
    char key = 'K';
    cout << "single test:" << (char)enc(c, key) << endl;

    bool problem = false;
    int k, ch;
    for(k=0;k<256;k++)
    {

        for(ch=0;ch<256;ch++)
        {
            if( enc( dec((unsigned char)ch, (unsigned char)k), k) != ch )
            {
                problem = true;
                cout << "error k=" << k << "c=" << ch
                     << "result=" <<  (unsigned int)enc( dec((unsigned char)ch, (unsigned char)key), (unsigned char)key) << endl;

            }
        }
    }
    if(problem) cout << "There was a problem." << endl;
    else cout << "There was no problem." << endl;
}