rsa加密解密C语言代码

以下是一个简单的C语言实现RSA加密解密的代码，其中包括生成密钥、加密和解密三个部分：

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

#define MAX 1000

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

int extend(int a, int b) {
    int x1 = 1, y1 = 0, x2 = 0, y2 = 1, x, y, r, q;
    while (b > 0) {
        q = a / b;
        r = a - q * b;
        x = x1 - q * x2;
        y = y1 - q * y2;
        a = b;
        b = r;
        x1 = x2;
        y1 = y2;
        x2 = x;
        y2 = y;
    }
    return x1;
}

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

int generate_prime() {
    int p;
    do {
        p = rand() % MAX;
    } while (!is_prime(p));
    return p;
}

void generate_key(int *p, int *q, int *n, int *t, int *e, int *d) {
    srand(time(NULL));
    *p = generate_prime();
    *q = generate_prime();
    *n = (*p) * (*q);
    *t = ((*p) - 1) * ((*q) - 1);
    do {
        *e = rand() % (*t - 2) + 2;
    } while (gcd(*e, *t) != 1);
    *d = extend(*e, *t);
}

int fast_pow(int a, int b, int n) {
    int ans = 1;
    while (b > 0) {
        if (b & 1) {
            ans = (ans * a) % n;
        }
        a = (a * a) % n;
        b >>= 1;
    }
    return ans;
}

void encrypt(int e, int n, char *plaintext, int *ciphertext) {
    int i;
    for (i = 0; i < strlen(plaintext); i++) {
        ciphertext[i] = fast_pow(plaintext[i], e, n);
    }
}

void decrypt(int d, int n, int *ciphertext, char *plaintext) {
    int i;
    for (i = 0; i < strlen(plaintext); i++) {
        plaintext[i] = fast_pow(ciphertext[i], d, n);
    }
}

int main() {
    int p, q, n, t, e, d, i;
    char plaintext[MAX];
    int ciphertext[MAX];
    generate_key(&p, &q, &n, &t, &e, &d);
    printf("公钥为：(%d, %d)\n", e, n);
    printf("私钥为：%d\n", d);
    printf("请输入要加密的明文：");
    scanf("%s", plaintext);
    encrypt(e, n, plaintext, ciphertext);
    printf("密文为：");
    for (i = 0; i < strlen(plaintext); i++) {
        printf("%d ", ciphertext[i]);
    }
    printf("\n请输入正确的密钥，密钥正确将解密上面的密文：");
    scanf("%d", &d);
    if (d == e) {
        decrypt(d, n, ciphertext, plaintext);
        printf("明文为：%s\n", plaintext);
    } else {
        printf("密钥错误，无法解密！\n");
    }
    return 0;
}

该代码实现了RSA加密解密的基本功能，包括生成密钥、加密和解密。用户可以输入要加密的明文，程序将输出密文，并要求用户输入正确的密钥进行解密。如果密钥正确，程序将输出解密后的明文，否则将输出密钥错误的提示信息。