Шифрование Вижинера

//---------------------------------------------------------------------------
 
#include <vcl.h>
#pragma hdrstop
 
#include "Unit1.h"
//---------------------------------------------------------------------------
#pragma package(smart_init)
#pragma resource "*.dfm"
TForm1 *Form1;
//---------------------------------------------------------------------------
__fastcall TForm1::TForm1(TComponent* Owner)
        : TForm(Owner)
{
Memo1->Clear();
Memo2->Clear();
Memo3->Clear();
Edit1->Clear();
}
//---------------------------------------------------------------------------
 
void __fastcall TForm1::Button1Click(TObject *Sender)
{
AnsiString textshifr,key;
int m;
textshifr=Memo1->Text;
key=Edit1->Text;
int j=1;
for (int i =1;i<=textshifr.Length();i++)
{
if(j>key.Length()) j=1;
m=((unsigned char)textshifr[i]) +((unsigned char)key[j]);
if (m >= 256)
m=m-255;
textshifr[i] =(char)m;
j++;
}
Memo2->Text = textshifr;
}
//---------------------------------------------------------------------------
 
void __fastcall TForm1::Button2Click(TObject *Sender)
{AnsiString textshifr,key;
int m;
textshifr=Memo2->Text;
int j=1;
for (int i=1;i<=textshifr.Length();i++)
{
if (j>key.Length()) j=1;
m=( ((unsigned char)textshifr[ i ] )- ((unsigned char)key[j]));
//if (m <= 0)
//m=m+255;
textshifr[ i ] = (char)m;
j++;
}
Memo3->Text =textshifr;
}
//---------------------------------------------------------------------------
void __fastcall TForm1::Button3Click(TObject *Sender)
{
Memo1->Clear();
Memo2->Clear();
Memo3->Clear();
Edit1->Clear();
}