C#对称加密（AES加密）每次生成的结果都不同的实现思路和代码实例

思路：使用随机向量，把随机向量放入密文中，每次解密时从密文中截取前16位，其实就是我们之前加密的随机向量。

 代码：

public static string encrypt(string plaintext, string aeskey)
{
  rijndaelmanaged rijndaelcipher = new rijndaelmanaged();
  byte[] inputbytearray = encoding.utf8.getbytes(plaintext);//得到需要加密的字节数组
  rijndaelcipher.key = convert.frombase64string(aeskey);//加解密双方约定好密钥：aeskey
  rijndaelcipher.generateiv();
  byte[] keyiv = rijndaelcipher.iv;
  byte[] cipherbytes = null;
  using (memorystream ms = new memorystream())
  {
    using (cryptostream cs = new cryptostream(ms, rijndaelcipher.createencryptor(), cryptostreammode.write))
    {
      cs.write(inputbytearray, 0, inputbytearray.length);
      cs.flushfinalblock();
      cipherbytes = ms.toarray();//得到加密后的字节数组
      cs.close();
      ms.close();
    }
  }
  var allencrypt = new byte[keyiv.length + cipherbytes.length];
  buffer.blockcopy(keyiv, 0, allencrypt, 0, keyiv.length);
  buffer.blockcopy(cipherbytes, 0, allencrypt, keyiv.length * sizeof(byte), cipherbytes.length);
  return convert.tobase64string(allencrypt);
}
 
public static string decrypt(string showtext, string aeskey)
{
  string result = string.empty;
  try
  {
    byte[] ciphertext = convert.frombase64string(showtext);
    int length = ciphertext.length;
    symmetricalgorithm rijndaelcipher = rijndael.create();
    rijndaelcipher.key = convert.frombase64string(aeskey);//加解密双方约定好的密钥
    byte[] iv = new byte[16];
    buffer.blockcopy(ciphertext, 0, iv, 0, 16);
    rijndaelcipher.iv = iv;
    byte[] decryptbytes = new byte[length - 16];
    byte[] passwdtext = new byte[length - 16];
    buffer.blockcopy(ciphertext, 16, passwdtext, 0, length - 16);
    using (memorystream ms = new memorystream(passwdtext))
    {
      using (cryptostream cs = new cryptostream(ms, rijndaelcipher.createdecryptor(), cryptostreammode.read))
      {
        cs.read(decryptbytes, 0, decryptbytes.length);
        cs.close();
        ms.close();
      }
    }
    result = encoding.utf8.getstring(decryptbytes).replace("\0", "");  ///将字符串后尾的'\0'去掉
  }
  catch { }
  return result;
}

调用：

string jiami = myaestools.encrypt(textbox1.text, "abcdefgh12345678abcdefgh12345678");
 
string jiemi = myaestools.decrypt(textbox3.text, "abcdefgh12345678abcdefgh12345678");