rsa文件加密c加加代码不用openssl库

RSA加密算法是一种非对称加密算法，使用公钥对数据进行加密，使用私钥对数据进行解密。以下是一个简单的C++代码示例，可以使用RSA算法对文件进行加密，不使用OpenSSL库：

#include <iostream>
#include <fstream>
#include <cstring>
#include <cstdlib>
#include <ctime>
#include <cmath>
using namespace std;

const int MAX = 1000;

// 欧几里德算法求最大公约数
int gcd(int a, int b) {
    if (b == 0) {
        return a;
    }
    return gcd(b, a % b);
}

// 扩展欧几里德算法求模反元素
int exgcd(int a, int b, int &x, int &y) {
    if (b == 0) {
        x = 1;
        y = 0;
        return a;
    }
    int d = exgcd(b, a % b, x, y);
    int t = x;
    x = y;
    y = t - a / b * y;
    return d;
}

// 生成大质数
int generate_prime(int n) {
    srand(time(NULL));
    while (true) {
        int p = rand() % n + n / 2;
        bool flag = true;
        for (int i = 2; i <= sqrt(p); i++) {
            if (p % i == 0) {
                flag = false;
                break;
            }
        }
        if (flag) {
            return p;
        }
    }
}

// 生成公钥和私钥
void generate_key(int &p, int &q, int &n, int &e, int &d) {
    p = generate_prime(MAX);
    q = generate_prime(MAX);
    n = p * q;
    int f = (p - 1) * (q - 1);
    e = 65537;
    while (gcd(f, e) != 1) {
        e++;
    }
    exgcd(e, f, d, n);
    d = (d % f + f) % f;
}

// RSA加密
void encrypt(const char *input_file, const char *output_file, int n, int e) {
    ifstream fin(input_file, ios::binary | ios::in);
    ofstream fout(output_file, ios::binary | ios::out);
    if (!fin.is_open() || !fout.is_open()) {
        return;
    }
    char buffer[MAX];
    while (!fin.eof()) {
        fin.read(buffer, MAX);
        int len = fin.gcount();
        for (int i = 0; i < len; i++) {
            int m = buffer[i];
            int c = 1;
            for (int j = 0; j < e; j++) {
                c = (c * m) % n;
            }
            fout.write((char *)&c, sizeof(int));
        }
    }
    fin.close();
    fout.close();
}

// RSA解密
void decrypt(const char *input_file, const char *output_file, int n, int d) {
    ifstream fin(input_file, ios::binary | ios::in);
    ofstream fout(output_file, ios::binary | ios::out);
    if (!fin.is_open() || !fout.is_open()) {
        return;
    }
    int buffer[MAX];
    while (!fin.eof()) {
        fin.read((char *)buffer, sizeof(int) * MAX);
        int len = fin.gcount() / sizeof(int);
        for (int i = 0; i < len; i++) {
            int c = buffer[i];
            int m = 1;
            for (int j = 0; j < d; j++) {
                m = (m * c) % n;
            }
            fout.write((char *)&m, sizeof(char));
        }
    }
    fin.close();
    fout.close();
}

int main() {
    int p, q, n, e, d;
    generate_key(p, q, n, e, d);
    cout << "p = " << p << endl;
    cout << "q = " << q << endl;
    cout << "n = " << n << endl;
    cout << "e = " << e << endl;
    cout << "d = " << d << endl;
    encrypt("input.txt", "output.txt", n, e);
    decrypt("output.txt", "input2.txt", n, d);
    return 0;
}

上述代码首先通过欧几里德算法求出最大公约数，再使用扩展欧几里德算法求出模反元素，进而生成公钥和私钥。然后通过文件输入输出流，读取需要加密的文件并加密后输出到输出文件中。最后再通过私钥对输出文件进行解密。