RC4 算法

简介

RC4 - 维基百科
没事水一水v🤣

代码

class RC4 {
public:
    RC4(const unsigned char *key, unsigned int key_len)
    {
        // 初始化S盒，临时T盒
        for (int i = 0; i < 256; i++) {
            _S[i] = i;
            _T[i] = key[i % key_len];
        }
            
        // 打乱S盒
        for (int i = 0, j = 0; i < 256; i++) {
            j = (j + _S[i] + _T[i]) % 256;
            unsigned char tmp = _S[i];
            _S[i] = _S[j];
            _S[j] = tmp;
        }
    }
    virtual ~RC4()
    {
    }

    unsigned int convert(unsigned char *ptr, unsigned int len)
    {
        int i = 0, j = 0;
        memcpy(_T, _S, 256);
        // 生成密钥流，进行加解密
        for(unsigned int k = 0; k < len; k++) {
            i = (i + 1) % 256;
            j = (j = _T[i]) % 256;
            unsigned char tmp = _T[i];
            _T[i] = _T[j];
            _T[j] = tmp;
            ptr[k] = ptr[k] ^ _T[(_T[i] + _T[j]) % 256];
        }
        return len;
    }

private:
    unsigned char _S[256]{ 0 };
    unsigned char _T[256]{ 0 };
};