DES шифрование

procedure TForm1.btnEncryptClick(Sender: TObject);
  var
    Cipher: TDCP_rc4;
    KeyStr: string;
    Source, Dest: TFileStream;
  begin
    KeyStr:= '';
    if InputQuery('Passphrase','Enter passphrase',KeyStr) then  // get the passphrase
    begin
      try
        Source:= TFileStream.Create(boxInputFile.Text,fmOpenRead);
        Dest:= TFileStream.Create(boxOutputFile.Text,fmCreate);
        Cipher:= TDCP_rc4.Create(Self);
        Cipher.InitStr(KeyStr,TDCP_sha1);              // initialize the cipher with a hash of the passphrase
        Cipher.EncryptStream(Source,Dest,Source.Size); // encrypt the contents of the file
        Cipher.Burn;
        Cipher.Free;
        Dest.Free;
        Source.Free;
        MessageDlg('File encrypted',mtInformation,[mbOK],0);
      except
        MessageDlg('File IO error',mtError,[mbOK],0);
      end;
    end;
  end;
  
  procedure TForm1.btnDecryptClick(Sender: TObject);
  var
    Cipher: TDCP_rc4;
    KeyStr: string;
    Source, Dest: TFileStream;
  begin
    KeyStr:= '';
    if InputQuery('Passphrase','Enter passphrase',KeyStr) then  // get the passphrase
    begin
      try
        Source:= TFileStream.Create(boxInputFile.Text,fmOpenRead);
        Dest:= TFileStream.Create(boxOutputFile.Text,fmCreate);
        Cipher:= TDCP_rc4.Create(Self);
        Cipher.InitStr(KeyStr,TDCP_sha1);              // initialize the cipher with a hash of the passphrase
        Cipher.DecryptStream(Source,Dest,Source.Size); // decrypt the contents of the file
        Cipher.Burn;
        Cipher.Free;
        Dest.Free;
        Source.Free;
        MessageDlg('File decrypted',mtInformation,[mbOK],0);
      except
        MessageDlg('File IO error',mtError,[mbOK],0);
      end;
    end;
  end;

Cipher: TDCP_rc4;