var Clave: string;
procedure TForm1.Edit1KeyPress(Sender: TObject; var Key: Char);
var Temp: string;
begin
if Key = #8 then
begin
if Length(Clave) <> 0 then
SetLength(Clave, Length(Clave) - 1);
end
else
if Key in ['0'..'9', 'a'..'z', 'A'..'Z'] then
begin
Clave := Clave + Key;
Key := Edit1.PasswordChar;
end
else
Key := #0;
end;