rsa加密算法c++语言代码

以下是RSA加密算法的C++语言代码示例：

#include <iostream>
#include <cmath>

using namespace std;

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

int modPow(int base, int exponent, int modulus) {
    int result = 1;
    while (exponent > 0) {
        if (exponent % 2 == 1) {
            result = (result * base) % modulus;
        }
        base = (base * base) % modulus;
        exponent = exponent / 2;
    }
    return result;
}

int main() {
    int p, q, n, phi, e, d, message, ciphertext, plaintext;

    // Step 1: Choose two prime numbers
    p = 17;
    q = 19;

    // Step 2: Compute n = p * q
    n = p * q;

    // Step 3: Compute phi(n) = (p - 1) * (q - 1)
    phi = (p - 1) * (q - 1);

    // Step 4: Choose an integer e such that 1 < e < phi(n)
    e = 5;
    while (gcd(e, phi) != 1) {
        e++;
    }

    // Step 5: Compute d such that d * e = 1 (mod phi(n))
    d = 1;
    while ((d * e) % phi != 1) {
        d++;
    }

    // Step 6: Encrypt the message using the public key (e, n)
    message = 123;
    ciphertext = modPow(message, e, n);
    cout << "Encrypted message: " << ciphertext << endl;

    // Step 7: Decrypt the ciphertext using the private key (d, n)
    plaintext = modPow(ciphertext, d, n);
    cout << "Decrypted message: " << plaintext << endl;

    return 0;
}

该示例实现了RSA加密算法的核心步骤，包括：

1. 选择两个质数 p 和 q
2. 计算 n = p * q
3. 计算 phi(n) = (p - 1) * (q - 1)
4. 选择一个整数 e 使得 1 < e < phi(n)，且 gcd(e, phi(n)) = 1
5. 计算 d 使得 d * e = 1 (mod phi(n))
6. 使用公钥 (e, n) 加密消息
7. 使用私钥 (d, n) 解密密文

在实际应用中，需要考虑到安全性和性能等因素，例如选择更大的质数和密钥长度等。