常用的加密字符串的方式有几种请用C加加示例一下

常用的加密字符串的方式有很多种，比如MD5、SHA1、SHA256、AES等。下面以AES加密为例，示例代码如下：

#include <iostream>
#include <string>
#include <cstring>
#include <openssl/aes.h>

using namespace std;

string aes_encrypt(string plain_text, string key) {
    AES_KEY aes_key;
    unsigned char iv[AES_BLOCK_SIZE];
    memset(iv, , AES_BLOCK_SIZE);
    if (AES_set_encrypt_key((const unsigned char*)key.c_str(), 128, &aes_key) < ) {
        return "";
    }
    int len = plain_text.length();
    int padding = AES_BLOCK_SIZE - len % AES_BLOCK_SIZE;
    len += padding;
    unsigned char* input = new unsigned char[len];
    memcpy(input, plain_text.c_str(), plain_text.length());
    for (int i = ; i < padding; i++) {
        input[plain_text.length() + i] = padding;
    }
    unsigned char* output = new unsigned char[len];
    AES_cbc_encrypt(input, output, len, &aes_key, iv, AES_ENCRYPT);
    string cipher_text((char*)output, len);
    delete[] input;
    delete[] output;
    return cipher_text;
}

int main() {
    string plain_text = "Hello, world!";
    string key = "1234567890123456";
    string cipher_text = aes_encrypt(plain_text, key);
    cout << "Plain text: " << plain_text << endl;
    cout << "Cipher text: " << cipher_text << endl;
    return ;
}

以上代码使用AES算法对字符串进行加密，其中key为密钥，plain_text为明文，cipher_text为密文。