rsa加密算法c++语言实现

RSA加密算法C语言实现需要用到大数运算库，可以使用GMP库来实现。以下是一个简单的RSA加密算法C语言实现的代码示例：

#include <stdio.h>
#include <stdlib.h>
#include <time.h>
#include <gmp.h>

void generate_key(mpz_t p, mpz_t q, mpz_t n, mpz_t e, mpz_t d)
{
    // Generate random prime numbers p and q
    gmp_randstate_t state;
    gmp_randinit_default(state);
    gmp_randseed_ui(state, time(NULL));
    mpz_t bit_size;
    mpz_init(bit_size);
    mpz_set_ui(bit_size, 1024);  // Set key size to 1024 bits
    mpz_t one;
    mpz_init(one);
    mpz_set_ui(one, 1);
    mpz_urandomb(p, state, bit_size);
    mpz_urandomb(q, state, bit_size);
    while (!mpz_probable_prime_p(p, state))
    {
        mpz_add(p, p, one);
    }
    while (!mpz_probable_prime_p(q, state))
    {
        mpz_add(q, q, one);
    }

    // Compute n
    mpz_mul(n, p, q);

    // Compute phi(n)
    mpz_t phi_n;
    mpz_init(phi_n);
    mpz_t p_minus_one;
    mpz_init(p_minus_one);
    mpz_sub_ui(p_minus_one, p, 1);
    mpz_t q_minus_one;
    mpz_init(q_minus_one);
    mpz_sub_ui(q_minus_one, q, 1);
    mpz_mul(phi_n, p_minus_one, q_minus_one);

    // Choose e
    mpz_t gcd;
    mpz_init(gcd);
    do
    {
        mpz_urandomm(e, state, phi_n);
        mpz_gcd(gcd, e, phi_n);
    } while (mpz_cmp_ui(gcd, 1) != 0);

    // Compute d
    mpz_invert(d, e, phi_n);
    gmp_randclear(state);
    mpz_clear(bit_size);
    mpz_clear(one);
    mpz_clear(phi_n);
    mpz_clear(p_minus_one);
    mpz_clear(q_minus_one);
    mpz_clear(gcd);
}

void rsa_encrypt(mpz_t m, mpz_t n, mpz_t e, mpz_t c)
{
    mpz_powm(c, m, e, n);
}

void rsa_decrypt(mpz_t c, mpz_t n, mpz_t d, mpz_t m)
{
    mpz_powm(m, c, d, n);
}

int main(void)
{
    // Generate key
    mpz_t p, q, n, e, d;
    mpz_init(p);
    mpz_init(q);
    mpz_init(n);
    mpz_init(e);
    mpz_init(d);
    generate_key(p, q, n, e, d);

    // Encrypt a message
    char message[] = "Hello, world!";
    mpz_t m, c;
    mpz_init(m);
    mpz_import(m, strlen(message), 1, sizeof(char), 0, 0, message);
    mpz_init(c);
    rsa_encrypt(m, n, e, c);
    gmp_printf("Encrypted message: %Zd\n", c);

    // Decrypt the message
    mpz_t m2;
    mpz_init(m2);
    rsa_decrypt(c, n, d, m2);
    size_t size;
    char* message2 = (char*)mpz_export(NULL, &size, 1, sizeof(char), 0, 0, m2);
    message2[size] = '\0';  // Add null terminator
    printf("Decrypted message: %s\n", message2);

    // Clean up
    mpz_clear(p);
    mpz_clear(q);
    mpz_clear(n);
    mpz_clear(e);
    mpz_clear(d);
    mpz_clear(m);
    mpz_clear(c);
    mpz_clear(m2);
    free(message2);
    return 0;
}