Looking for Ideas in Time clock program software

Hi Experts,

I have a program that keeps information on time clock for employees daily schedule.

Each employee enters their name/initials and clicks a button that automatically saves the date/time user came and left.

Now our manager is concerned about fraudulent entries, meaning some employees will ask their friends to open the system and click for them..

Any idea how I can build in a security logic into the system to prevent this?

P.S. I know there are ready packages in the market with face/fingers recognition etc.. just wonder if we can make up something w/o the need to switch to third party software.