How to use finger security in bio metric base (Thumb recognition) voting app??

[AC Question]

I want to use finger security in my app, first it take thumb prints and save them in database and after this, when some one cast his/her vote using my app, it first take thumb prints and match them with existing database, if it matches it allows to cast vote and if it doesn't match then access denied. how i can use finger security in my app.. any suggestion?? some sort of source code help..