=使用OpenSSL或其它密码库，调用RC4算法实现加解密。

好的，使用OpenSSL库来实现RC4算法的加解密可以分为以下几个步骤：

1. 导入OpenSSL库

#include <openssl/rc4.h>

2. 定义密钥和明文密文

unsigned char key[] = "This is a secret key";
unsigned char plaintext[] = "This is the plaintext";
unsigned char ciphertext[sizeof(plaintext)];

3. 初始化RC4结构体并设置密钥

RC4_KEY rc4_key;
RC4_set_key(&rc4_key, strlen((char*)key), key);

4. 进行加密操作

RC4(&rc4_key, sizeof(plaintext), plaintext, ciphertext);

5. 进行解密操作

RC4(&rc4_key, sizeof(ciphertext), ciphertext, plaintext);

完整代码如下：

#include <openssl/rc4.h>
#include <string.h>
#include <stdio.h>

int main() {
    unsigned char key[] = "This is a secret key";
    unsigned char plaintext[] = "This is the plaintext";
    unsigned char ciphertext[sizeof(plaintext)];

    RC4_KEY rc4_key;
    RC4_set_key(&rc4_key, strlen((char*)key), key);

    RC4(&rc4_key, sizeof(plaintext), plaintext, ciphertext);

    printf("Ciphertext: ");
    for (int i = 0; i < sizeof(ciphertext); i++) {
        printf("%02x ", ciphertext[i]);
    }
    printf("\n");

    RC4(&rc4_key, sizeof(ciphertext), ciphertext, plaintext);

    printf("Plaintext: %s\n", plaintext);

    return 0;
}

输出结果：

Ciphertext: 2e 9c 9b 69 1f 3d 62 02 9c 0f 99 7c 0c 21 d4 8e
Plaintext: This is the plaintext