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("", ""); ///将字符串后尾的''去掉 } catch { } return result; }

调用：

string jiaMi = MyAESTools.Encrypt(textBox1.Text, "abcdefgh12345678abcdefgh12345678"); string jieMi = MyAESTools.Decrypt(textBox3.Text, "abcdefgh12345678abcdefgh12345678");