More Robust Twinning Between Secret Field Input Pairs

This JS code doesn't seem robust/stable at all:

$(this).val($('.form-field-secret-concealed input', $(this).parent().parent()).val());
$('.form-field-secret-concealed input', $(this).parent().parent()).val($(this).val());

Any changes in the theme function of text fields could break it (ex. With BH Bootstrap theme)

More proper selectors need to be given to make selection of the pair more robust.