Whatever said above by Rahul is correct which everybody should remember. I know a IT Consultancy firm in Bangalore which at the time of appointment asks the joining employees to sign a service agreement for 2 years & deposit their original academic certificates. The certificates are returned to the employees once the agreement term gets expired.
Handing over your original certicates your employer or anybody else may land you in trouble. You can produce the original certificates only for verification, but ensure to get it back immediately. The intention may not always be to hold back the certificates, but in case they are misplaced, it will take you ages to get a duplicate one from the concerned University/Institute.
Always remember....never handover your original certificates to anyone.......