PROGRAM ENSKRIPSI DAN DESKRIPSI C#

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;

namespace ConsoleApplication1
{
    class Program
    {
        static void Main(string[] args)
        {
        enkripsi:
            Console.Clear();
            Console.WriteLine("ENKRIPSI");
            Console.WriteLine();
            Console.Write("input  : ");
            string input = Console.ReadLine();          
            char [] kata = input.ToCharArray();
            string hsl ="";
          
            for (int i = 0 ; i < input.Length ; i++)
            {
               
                switch (kata[i])
                {
                    case 'z':
                        kata[i] = 'b';
                        kata[i]--;
                        kata[i]--;
                        break;
                    case 'Z':
                        kata[i] = 'B';
                        kata[i]--;
                        kata[i]--;
                        break;
                    case 'y':
                        kata[i] = 'a';
                        kata[i]--;
                        kata[i]--;
                        break;
                    case 'Y':
                        kata[i] = 'A';
                        kata[i]--;
                        kata[i]--;
                        break;
                    case ' ':
                        kata[i] = ' ';
                        kata[i]--;
                        kata[i]--;
                        break;
                }
                kata[i]++;
                kata[i]++;
                hsl = hsl + kata[i];
            }
                Console.WriteLine("output : {0}",hsl);
                Console.ReadLine();
                Console.WriteLine();
                Console.WriteLine("DEKRIPSI");
                Console.WriteLine();   
            Console.Write("input  : ");
                input = Console.ReadLine();
               kata = input.ToCharArray();
                hsl = "";

                for (int i = 0; i < input.Length; i++)
                {
                    switch (kata[i])
                    {
                        case 'b':
                            kata[i] = 'z';
                            kata[i]++;
                            kata[i]++;
                            break;
                        case 'B':
                            kata[i] = 'Z';
                            kata[i]++;
                            kata[i]++;
                            break;
                        case 'a':
                            kata[i] = 'y';
                            kata[i]++;
                            kata[i]++;
                            break;
                        case 'A':
                            kata[i] = 'Y';
                            kata[i]++;
                            kata[i]++;
                            break;
                          

                            case ' ' :
                            kata[i] = ' ';
                            kata[i]++;
                            kata[i]++;
                            break;
                    }
                    kata[i]--;
                    kata[i]--;
                    hsl = hsl + kata[i];
                }
                Console.WriteLine("output : {0}", hsl);
                Console.ReadKey();
                goto enkripsi;


        }
    }
}