Hi Raghu

you should read the following articles..
Extracting the flash data from an P89c51RD2 is childs play for these people...its a real eye opener with the only conclusion is that nothing is safe...especially the P89c51RD2 type .

http://www.cl.cam.ac.uk/users/rja14/

and the classic tamper resistance article

http://www.cl.cam.ac.uk/users/rja14/tamper.html