Fungsi Enskripsi & Deskripsi

#include <cstdlib>
#include <iostream>
#include <math.h>
#include <string.h>

using namespace std;

int main(int argc, char *argv[])
{
    lagi:
    char plain[100];
    char chiper[100];
    int key;
    int pilih;
    cout << "Masukkan Pillihan  " << endl;
    cout << "1. Enkripsi" << endl;
    cout << "2. deskripsi" << endl;
    cout << "Masukkan sidini : ";
    cin >> pilih;
    if(pilih=1){
    cout << "Enkripsi " << endl       ;
    cout << "Masukkan kata : ";
    cin >> plain;
    cout << "Masukkan Key nya : ";
    cin >> key;
   
    for(int i=0;i<strlen(plain);i++){
            //cout << plain[i] << "(" << int (plain[i]) << ")";
            chiper[i]=((plain[i]+key)%128);
 
            }
           
           
    for(int i=0;i<strlen(chiper);i++){
            cout << endl;
            cout << chiper[i];
            cout << endl;
            }
            }
    else{
           
    cout << "Deskripsi :" << endl       ;
    cout << "Masukkan kata : ";
    cin >> plain;
    cout << "Masukkan Key nya : ";
    cin >> key;
    cout << "Enkripsi :"        ;
    for(int i=0;i<strlen(chiper);i++){
            //cout << chiper[i] << "(" << int (chiper[i]) << ")";
            plain[i]=((chiper[i]-key)%128);

 
            }
           
           
    for(int i=0;i<strlen(plain);i++){
            cout << endl;
            cout << plain[i];
            cout << endl;
            }
}

/*cout << "Pilih lagi?? " << endl;
cout << "tekan y jika Ya, tekan n jika tidak " << endl;
char a;
char y, Y;
cin >> a;

if(a==y||a==Y){
               goto lagi;
               }
               else{
                    cout << "terima kasih" << endl;
                        system("PAUSE");
    return EXIT_SUCCESS;

                   
                    }*/
                   
    system("PAUSE");
    return EXIT_SUCCESS;
}