c++实现 RC4加密算法

RC4加密算法是一种流密码算法，它可以用于数据的加密和解密。下面是一个用C语言实现RC4加密算法的示例代码：

#include <stdio.h>
#include <stdlib.h>

void swap(unsigned char *a, unsigned char *b) {
    unsigned char temp = *a;
    *a = *b;
    *b = temp;
}

void rc4_init(unsigned char *key, int key_length, unsigned char S[256]) {
    for (int i = 0; i < 256; i++) {
        S[i] = i;
    }

    int j = 0;
    for (int i = 0; i < 256; i++) {
        j = (j + S[i] + key[i % key_length]) % 256;
        swap(&S[i], &S[j]);
    }
}

void rc4_crypt(unsigned char *input, unsigned char *output, int input_length, unsigned char S[256]) {
    int i = 0;
    int j = 0;

    for (int k = 0; k < input_length; k++) {
        i = (i + 1) % 256;
        j = (j + S[i]) % 256;
        swap(&S[i], &S[j]);
        int t = (S[i] + S[j]) % 256;
        output[k] = input[k] ^ S[t];
    }
}

int main() {
    unsigned char key[] = "ThisIsMyKey";
    unsigned char plaintext[] = "Hello, world!";
    int key_length = sizeof(key) - 1;
    int plaintext_length = sizeof(plaintext) - 1;

    unsigned char S[256];
    rc4_init(key, key_length, S);

    unsigned char ciphertext[plaintext_length];
    rc4_crypt(plaintext, ciphertext, plaintext_length, S);

    printf("Plaintext: %s\n", plaintext);
    printf("Ciphertext: ");
    for (int i = 0; i < plaintext_length; i++) {
        printf("%02X ", ciphertext[i]);
    }
    printf("\n");

    return 0;
}

在上面的示例代码中，`rc4_init`函数用于初始化RC4算法，`rc4_crypt`函数用于加密或解密数据。你可以直接运行这段代码，它将输出明文和加密后的密文。请注意，这只是一个简单的示例，实际使用时需要考虑密钥的生成和安全性等问题。