using System;  

using System.IO;  

using System.Security.Cryptography;  

using System.Text; 

public class Program

{

    public static void Main()

    {

                    //var key = "b14ca5898a4e4133bbce2ea2315a1916";  

        var key = Guid.NewGuid().ToString().Replace("-","") ;// "abcdef1234567890";  

        DateTime n = DateTime.Now;

        Console.WriteLine(n.ToString());

        string sTicks = n.Ticks.ToString();

        Console.WriteLine(sTicks);

        DateTime myDate = new DateTime(long.Parse(sTicks));

        Console.WriteLine(myDate);

        Console.WriteLine(myDate.Ticks);

            Console.WriteLine(key);  

            Console.WriteLine(key.Length);  

            //Console.WriteLine("Please enter a secret key for the symmetric algorithm.");  

            //var key = Console.ReadLine();  

            Console.WriteLine("Please enter a string for encryption");  

            var str = "Please enter a string for encryption Please enter a string for encryption Please enter a string for encryption";// Console.ReadLine();  

            var encryptedString = AesOperation.EncryptString(key, str);  

            Console.WriteLine($"encrypted string = {encryptedString}");  

            var decryptedString = AesOperation.DecryptString(key, encryptedString);  

            Console.WriteLine($"decrypted string = {decryptedString}");  

    }

}

​

    public class AesOperation  

    {  

        public static string EncryptString(string key, string plainText)  

        {  

            byte[] iv = new byte[16];  

            byte[] array;  

            using (Aes aes = Aes.Create())  

            {  

                aes.Key = Encoding.UTF8.GetBytes(key);  

                aes.IV = iv;  

                ICryptoTransform encryptor = aes.CreateEncryptor(aes.Key, aes.IV);  

                using (MemoryStream memoryStream = new MemoryStream())  

                {  

                    using (CryptoStream cryptoStream = new CryptoStream((Stream)memoryStream, encryptor, CryptoStreamMode.Write))  

                    {  

                        using (StreamWriter streamWriter = new StreamWriter((Stream)cryptoStream))  

                        {  

                            streamWriter.Write(plainText);  

                        }  

                        array = memoryStream.ToArray();  

                    }  

                }  

            }  

            return Convert.ToBase64String(array);  

        }  

        public static string DecryptString(string key, string cipherText)  

        {  

            byte[] iv = new byte[16];  

            byte[] buffer = Convert.FromBase64String(cipherText);  

            using (Aes aes = Aes.Create())  

            {  

                aes.Key = Encoding.UTF8.GetBytes(key);  

                aes.IV = iv;  

                ICryptoTransform decryptor = aes.CreateDecryptor(aes.Key, aes.IV);  

                using (MemoryStream memoryStream = new MemoryStream(buffer))  

                {  

                    using (CryptoStream cryptoStream = new CryptoStream((Stream)memoryStream, decryptor, CryptoStreamMode.Read))  

                    {  

                        using (StreamReader streamReader = new StreamReader((Stream)cryptoStream))  

                        {  

                            return streamReader.ReadToEnd();  

                        }  

                    }  

                }  

            }  

        }  

    }