Are you talking voter ID? If so, look at it this way. You go to the hospital to have a baby, 30 other women are there who just had their baby or are in the process of having one just like you. You have your baby. They don't ID it. 6 hours later the second shift nurse brings a baby to you. How do you know it's yours? You don't unless it is wearing an ID bracelet all baby's get before they leave the delivery room.
All you want to know with voter ID is that the voter belongs to the country it is voting in.