AES解密

/// <summary>
    /// 解密帮助类
    /// </summary>
    public class EncryptHelper
    {        
        #region AES解密函数
        /// <summary>AES解密</summary>  
        /// <param name="text">密文</param>  
        /// <returns>明文</returns>  
        public static string Decrypt(string secretKey, string iv, string text)
        {
            RijndaelManaged rijndaelCipher = new RijndaelManaged();
            rijndaelCipher.Mode = CipherMode.CBC;
            rijndaelCipher.Padding = PaddingMode.None;
            rijndaelCipher.KeySize = 128;
            rijndaelCipher.BlockSize = 128;
            byte[] encryptedData = Convert.FromBase64String(text);
            byte[] pwdBytes = System.Text.Encoding.UTF8.GetBytes(secretKey);
            //取byte数组前16位做key
            byte[] keyBytes = new byte[16];
            int len = pwdBytes.Length;
            if (len > keyBytes.Length)
                len = keyBytes.Length;
            System.Array.Copy(pwdBytes, keyBytes, len);
            rijndaelCipher.Key = keyBytes;
            //取sendTime补A到16位做IV
            rijndaelCipher.IV = Encoding.UTF8.GetBytes("KA"+iv);
            ICryptoTransform transform = rijndaelCipher.CreateDecryptor();
            byte[] plainText = transform.TransformFinalBlock(encryptedData, 0, encryptedData.Length);
            return Encoding.UTF8.GetString(plainText);
        }
        #endregion
    }