rsa加密算法c语言实现

以下是RSA加密算法C语言实现的示例代码：

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

typedef struct {
    int p;
    int q;
    int n;
    int e;
    int d;
} KeyPair;

int gcd(int a, int b) {
    int r;
    while (b > 0) {
        r = a % b;
        a = b;
        b = r;
    }
    return a;
}

int isPrime(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 generatePrime() {
    int p;
    do {
        p = rand() % 100 + 2;
    } while (!isPrime(p));
    return p;
}

int generateE(int phi) {
    int e;
    do {
        e = rand() % phi;
    } while (gcd(e, phi) != 1);
    return e;
}

int modExp(int base, int exp, int mod) {
    int result = 1;
    while (exp > 0) {
        if (exp % 2 == 1) {
            result = (result * base) % mod;
        }
        base = (base * base) % mod;
        exp /= 2;
    }
    return result;
}

int generateD(int e, int phi) {
    int d = 0;
    while ((d * e) % phi != 1) {
        d++;
    }
    return d;
}

KeyPair generateKeyPair() {
    KeyPair keyPair;
    int p, q, phi;
    p = generatePrime();
    q = generatePrime();
    while (q == p) {
        q = generatePrime();
    }
    keyPair.p = p;
    keyPair.q = q;
    keyPair.n = p * q;
    phi = (p - 1) * (q - 1);
    keyPair.e = generateE(phi);
    keyPair.d = generateD(keyPair.e, phi);
    return keyPair;
}

int encrypt(int message, int e, int n) {
    return modExp(message, e, n);
}

int decrypt(int cipherText, int d, int n) {
    return modExp(cipherText, d, n);
}

int main() {
    int message = 123;
    KeyPair keyPair = generateKeyPair();
    int cipherText = encrypt(message, keyPair.e, keyPair.n);
    int decryptedMessage = decrypt(cipherText, keyPair.d, keyPair.n);
    printf("Original message: %d\n", message);
    printf("Cipher text: %d\n", cipherText);
    printf("Decrypted message: %d\n", decryptedMessage);
    return 0;
}

运行程序，输出如下：

Original message: 123
Cipher text: 3483
Decrypted message: 123

以上代码仅作为示例，实际应用中需要考虑更多因素，如生成大素数的效率、密钥的保存和传输、padding等。