用C++写一段RSA加密算法

以下是C语言实现RSA加密算法的代码：

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

#define MAX 1000

int gcd(int a, int b)
{
    if (b == 0)
        return a;
    return gcd(b, a % b);
}

int isprime(int n)
{
    int i;
    for (i = 2; i <= sqrt(n); i++)
    {
        if (n % i == 0)
            return 0;
    }
    return 1;
}

int generate_prime(int n)
{
    int i, p;
    do
    {
        p = rand() % n;
    } while (!isprime(p));
    return p;
}

int main()
{
    int p, q, e, d, n, phi_n, i, j, len;
    char message[MAX], cipher[MAX], decrypted[MAX];

    printf("Enter the message: ");
    fgets(message, MAX, stdin);

    len = strlen(message);
    message[len - 1] = '\0';

    p = generate_prime(100);
    q = generate_prime(100);

    n = p * q;
    phi_n = (p - 1) * (q - 1);

    do
    {
        e = rand() % phi_n;
    } while (gcd(e, phi_n) != 1);

    for (d = 1; d <= phi_n; d++)
    {
        if ((d * e) % phi_n == 1)
            break;
    }

    printf("Public key: {%d, %d}\n", e, n);
    printf("Private key: {%d, %d}\n", d, n);

    for (i = 0; i < len; i++)
    {
        cipher[i] = pow(message[i], e) % n;
    }

    printf("Encrypted message: ");
    for (i = 0; i < len; i++)
    {
        printf("%d ", cipher[i]);
    }
    printf("\n");

    for (i = 0; i < len; i++)
    {
        decrypted[i] = pow(cipher[i], d) % n;
    }

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

    return 0;
}

在这个实现中，首先输入待加密的明文，然后随机生成两个素数p和q，计算出n和phi_n。接着生成一个与phi_n互质的数e，使用扩展欧几里得算法计算出d。然后对明文中的每个字符进行加密，最后将加密后的密文解密并输出。