need help on hardisk encryption (hardware)

Hi,
Our system is a DVR (set top box) working on sigma designs
smp8634
board with
linux 2.6 kernel.
The OS will boot form the flash on the board.
A hard disk is interfaced with the board. The DVR apparently has a
record option
which when opted for should record the digital stream into the hard
disk.
I want that digital data to be encrypted when being written and
decrypted when being read from the hard disk.

I'm specifically inclined to using hardware hard disk encryption as
using software would
degrade the performance of the system.


I will be glad if you reply with a solution for this.


Thanks in advance