how to protect directory from unauthorized access under linux

[Serge]

Hello there,
In one of my projects I have to protect specific directory on linux from
unauthorized access, that directory should be not accessible either in
single user mode or by booting server from live cd. In the same time
data must be completely open in runlevel 3.

That server will run at ISP hosting farm,  I can't put password on boot.
Any ideas how to implement this?

Thanks, Serge.