program c++ caesar chiper

#include <cstdlib>
#include <iostream>
#include <string.h>
#define maks 500

using namespace std;

class Enkripsi{
public:
Enkripsi();
void enkripsi();
void deskripsi();
void output();
private:
char chiper[maks];
int key;
char plain[maks];
};
Enkripsi::Enkripsi(){
cout<<"get a word : ";
cin.getline(chiper,sizeof(chiper));
cout<<"get the key :";
cin>>key;
cout<<endl;
}
void Enkripsi::enkripsi(){
for(int i=0;i<strlen(chiper); i+=1){
cout<<chiper[i]<<"("<<int(chiper[i])<<")";
chiper[i]=(chiper[i]+key)%128;
}
}
void Enkripsi::deskripsi(){
for(int i=0;i<strlen(chiper);i+=1){
plain[i]=(chiper[i]-key)%128;
chiper[i]=plain[i];
}
}
void Enkripsi::output(){
for(int i=0;i<strlen(chiper);i+=1){
cout<<chiper[i];
}
}

int main(int argc, char *argv[])
{
Enkripsi Deskripsi;
Deskripsi.enkripsi();
cout<<"\n\nAfter the encryption : ";
Deskripsi.output();
Deskripsi.deskripsi();
cout<<"\n\nback in the description: ";
Deskripsi.output();
cout<<endl;

system("PAUSE");
return EXIT_SUCCESS;
}