using System;

using System.IO;

using System.Text;

using System.Security.Cryptography;

public class Program

{

    public static void Main()

    {

        var key = "abcd1234";

        var salt = "4321";

        var encrypted = "";

        var decrypted = "";

        var alphabets = "ABCDEFGHIJKLMNOPQRSTUVWXYZ".ToCharArray();

        for (var i = 0; i < 100; i++)

        {

            var text = $"{Math.Floor((double)i / 10)}{i % 10}";

            encrypted = DesEncrypt(text, key, salt);

            decrypted = DesDecrypt(encrypted, key, salt);

            Console.WriteLine($"Text: {text} | Encrypted: {encrypted} | Decrypted: {decrypted}");

        }

    }

    private static string DesEncrypt(string plaintText, string strKey, string salt)

    {

        byte[] key = { }; //Encryption Key   

        byte[] IV = { 10, 20, 30, 40, 50, 60, 70, 80 };

        byte[] inputByteArray;

​

        try

        {

            key = Encoding.UTF8.GetBytes(strKey);

            // DESCryptoServiceProvider is a cryptography class defind in c#.  

            DESCryptoServiceProvider ObjDES = new DESCryptoServiceProvider();

            inputByteArray = Encoding.UTF8.GetBytes(plaintText + salt);

            MemoryStream Objmst = new MemoryStream();

            CryptoStream Objcs = new CryptoStream(Objmst, ObjDES.CreateEncryptor(key, IV), CryptoStreamMode.Write);

            Objcs.Write(inputByteArray, 0, inputByteArray.Length);

            Objcs.FlushFinalBlock();

​

            return Convert.ToBase64String(Objmst.ToArray());//encrypted string  

        }

        catch (System.Exception ex)

        {

            throw ex;

        }

    }

    private static string DesDecrypt(string cipherText, string strKey, string salt)

    {

        byte[] key = { };// Key   

        byte[] IV = { 10, 20, 30, 40, 50, 60, 70, 80 };

        byte[] inputByteArray = new byte[cipherText.Length];

​

        try

        {

            key = Encoding.UTF8.GetBytes(strKey);

            DESCryptoServiceProvider ObjDES = new DESCryptoServiceProvider();

            inputByteArray = Convert.FromBase64String(cipherText);

​

            MemoryStream Objmst = new MemoryStream();

            CryptoStream Objcs = new CryptoStream(Objmst, ObjDES.CreateDecryptor(key, IV), CryptoStreamMode.Write);

            Objcs.Write(inputByteArray, 0, inputByteArray.Length);

            Objcs.FlushFinalBlock();

​

            Encoding encoding = Encoding.UTF8;

            return encoding.GetString(Objmst.ToArray()).TrimEnd(salt.ToCharArray());

        }

        catch (System.Exception ex)

        {

            if (ex is FormatException) Console.WriteLine("The token is in the wrong format");

            if (ex is System.Security.Cryptography.CryptographicException) Console.WriteLine("Invalid token");

            throw ex;

        }

    }

}

​