rc4加密算法c++

以下是一个简单的 RC4 加密算法的 C++ 实现：

#include <iostream>
#include <cstring>

using namespace std;

class RC4 {
private:
    unsigned char S[256];
    unsigned int i, j;
public:
    RC4(unsigned char* key, int keylen) {
        for (int i = 0; i < 256; i++) {
            S[i] = i;
        }
        j = 0;
        for (int i = 0; i < 256; i++) {
            j = (j + S[i] + key[i % keylen]) % 256;
            swap(S[i], S[j]);
        }
        i = j = 0;
    }
    void encrypt(unsigned char* data, int datalen) {
        for (int k = 0; k < datalen; k++) {
            i = (i + 1) % 256;
            j = (j + S[i]) % 256;
            swap(S[i], S[j]);
            data[k] ^= S[(S[i] + S[j]) % 256];
        }
    }
};

int main() {
    unsigned char key[] = "this is a key";
    unsigned char data[] = "hello world";
    int keylen = strlen((char*)key);
    int datalen = strlen((char*)data);

    RC4 rc4(key, keylen);
    rc4.encrypt(data, datalen);

    cout << "Encrypted data: " << data << endl;

    rc4 = RC4(key, keylen);
    rc4.encrypt(data, datalen);

    cout << "Decrypted data: " << data << endl;

    return 0;
}

使用该算法可以对任意长度的数据进行加密和解密。可以自定义密钥和数据，加密后输出加密后的数据，再将加密后的数据解密，输出解密后的数据。