c++凯撒加密的破解代码

凯撒加密是一种很古老的加密算法，容易被破解。以下是C++语言下的凯撒加密破解代码：

#include <iostream>
#include <string>

using namespace std;

// 凯撒加密
string encrypt(string plaintext, int key) {
    string ciphertext = "";
    for (int i = 0; i < plaintext.length(); i++) {
        if (isalpha(plaintext[i])) {
            char c = plaintext[i];
            if (isupper(c)) {
                c = (c + key - 65) % 26 + 65;
            }
            else {
                c = (c + key - 97) % 26 + 97;
            }
            ciphertext += c;
        }
        else {
            ciphertext += plaintext[i];
        }
    }
    return ciphertext;
}

// 凯撒解密
string decrypt(string ciphertext, int key) {
    string plaintext = "";
    for (int i = 0; i < ciphertext.length(); i++) {
        if (isalpha(ciphertext[i])) {
            char c = ciphertext[i];
            if (isupper(c)) {
                c = (c - key - 65 + 26) % 26 + 65;
            }
            else {
                c = (c - key - 97 + 26) % 26 + 97;
            }
            plaintext += c;
        }
        else {
            plaintext += ciphertext[i];
        }
    }
    return plaintext;
}

// 破解凯撒加密
string decrypt_caesar(string ciphertext) {
    string plaintext = "";
    for (int key = 0; key < 26; key++) {
        plaintext = decrypt(ciphertext, key);
        cout << "key = " << key << " plaintext = " << plaintext << endl;
    }
    return plaintext;
}

int main() {
    string ciphertext = "Khoor, zruog!";
    string plaintext = decrypt_caesar(ciphertext);
    return 0;
}

以上代码演示了如何对凯撒加密进行破解。假设我们已知密文是“Khoor, zruog!”，我们可以通过枚举所有可能的密钥（0-25）来尝试解密。最终，我们找到了正确的密钥（3），并成功地解密了原始文本（Hello, world!）。