By James Grant, Team Lead and Senior Developer
When big stores started using digitizing pads to capture my signature for purchases, I had my usual paranoid reaction. No way! Think of all the ways it could go wrong:
1) My signature is stolen, gets applied to some other purchase, and I have no proof I didn't buy it
2) The store computer captures the purchase amount incorrectly and I get charged $150 instead of $15 for a watch
2) The store charges me twice when I purchased once
3) The store intentionally alters the price and I have no legal recourse
Signing for a computer – it's not the same
The beauty of signing on paper is you sign the same piece of paper that shows your purchase amount. You get a copy, they get a copy. In case of dispute, you each have evidence. The store cannot alter the amount without the risk of a detective discovering the alteration. They cannot apply that signature to another purchase. Also, it is a system that has worked reasonably well for decades and I have already accepted the risk.
When you sign on a pad or a "screen", most of them display the amount of your purchase, but when you hit the "OK" button, your signature gets stored in one computer file and the purchase amount gets stored in another (I expect, though I've never built or audited one of these). From my understanding of databases, I expect all these PoS (point of sale) systems record a transaction, and record the amount and the name of the file that contains the signature.
All four nightmare scenarios are possible
The computers used to handle sales are very much like the computer you use at home. They store information digitally and files get moved around from one computer to another. Sales computers can have software bugs, just as home computer software or voting machines can. I have been accidentally charged twice (it was an over-the-phone order), by an employee using a computer he didn't understand. I have no experience with a store intentionally defrauding me, but I have been a victim of credit card fraud, so it is no stretch to think a criminal would take my signature and use it if they could get hold of it.
So initially, I resisted using the signature pads. I asked to sign paper. At the start, when the pads were new, the stores still had the ability to print a paper receipt for me to sign, so I got my way. I noticed an increasing resistence however. I also noticed how my wife would roll her eyes, so I knew I needed to work out a compromise.
One day, when asked to sign on the pad, I tried an experiment. I discreetly wrote the purchase price in the corner of the screen and signed in the middle. Accepted! So I kept it up. Before long, I was in the habit of putting the purchase price at the top in the middle and intentionally signing so that my signature overlapped the numbers.
Once I saw that being accepted, I decided my problem was solved. It address three of the four worries I listed at the top and I can't imagine a thief going so far as erasing the numbers in an attempt to isolate my signature – that is pretty extreme.
So for anyone out there who has been nervous about the adoption of digital signature pads, try what I do: write the purchase amount first, then sign over it.