using System;

using System.IO;  

using System.Security.Cryptography;  

using System.Text;  

public class Program

{

    public static void Main()

    {

        Console.WriteLine("Hello World");

        var key = "b14ca5898a4e4133bbce2ea2315a1916";  

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

            //var key = Console.ReadLine();  

        var str = "Hello World";  

        var encryptedString = EncryptString(key, str);  

        Console.WriteLine("encrypted string = "+encryptedString);

​

        var decryptedString = DecryptString(key, encryptedString);  

        Console.WriteLine("decrypted string = "+decryptedString); 

    }

    public static string EncryptString(string key, string plainText)  

        {  

            byte[] iv = new byte[16];

            Console.WriteLine("Iv ="+iv);

            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();  

                        }  

                    }  

                }  

            }  

        }

}