rc4密码算法c语言代码

以下是RC4密码算法的C语言代码实现：

#include <stdio.h>
#include <string.h>

#define swap(a, b) ((a) ^= (b), (b) ^= (a), (a) ^= (b))

void RC4(unsigned char* pKey, unsigned long ulKeyLength, unsigned char* pData, unsigned long ulDataLength)
{
    unsigned char ucBox[256], ucTmp;
    int i, j = 0;

    for (i = 0; i < 256; i++) {
        ucBox[i] = i;
    }

    for (i = 0; i < 256; i++) {
        j = (j + ucBox[i] + pKey[i % ulKeyLength]) % 256;
        swap(ucBox[i], ucBox[j]);
    }

    i = j = 0;
    for (int k = 0; k < ulDataLength; k++) {
        i = (i + 1) % 256;
        j = (j + ucBox[i]) % 256;
        swap(ucBox[i], ucBox[j]);

        ucTmp = pData[k] ^ ucBox[(ucBox[i] + ucBox[j]) % 256];
        pData[k] = ucTmp;
    }
}

int main()
{
    unsigned char key[] = "1234567890";
    unsigned char data[] = "Hello World!";
    unsigned long key_len = strlen(key);
    unsigned long data_len = strlen(data);

    RC4(key, key_len, data, data_len);

    printf("Encrypted data: %s\n", data);

    RC4(key, key_len, data, data_len);

    printf("Decrypted data: %s\n", data);

    return 0;
}

该代码实现了RC4密码算法的加密和解密功能。在main函数中，我们使用字符串“1234567890”作为密钥，字符串“Hello World!”作为待加密的数据。加密和解密的过程分别通过调用RC4函数实现。最后输出解密后的数据，即可验证加密和解密的正确性。