For security I want to enable wallet.dat reading only by bitcoin client (or maybe archiver). I created group 'bitcoin'
and try
  chgrp bitcoin /usr/bin/bitcoin
  chmod g+s /usr/bin/bitcoin
  chgrp bitcoin /home/frodoj/.bitcoin/wallet.dat
  chmod 060 /home/frodo/.bitcoin/wallet.dat
but if I call bitcoin client, it crash:
==============================
(process:6472): Gtk-WARNING **: This process is currently running setuid or setgid.
This is not a supported use of GTK+. You must create a helper
program instead. For further details, see:

    http://www.gtk.org/setuid.html

Refusing to initialize GTK+.
17:46:08: Debug: In file ../src/unix/threadpsx.cpp at line 253: 'pthread_mutex_destroy()' failed with error 0x00000010 (Device or resource busy).
==============================
Is way to solve it?
When will bitcoin client works on encrypted wallet.dat?