Interesting way to acquire someone’s signature

From Simson Garfinkel’s “Absolute Identification“, chapter 3 of Database Nation:

Already, the United Parcel Service, the nation’s largest package delivery service, is also the nation’s leader in biometric piracy. For most packages, UPS requires that a signature be written to serve as proof of delivery. In 1987, UPS started scanning the pen-and-ink signatures recorded for each package delivery. These images were stored in a database and faxed to any person who called UPS’s 800 number and asked for a ‘proof of delivery’ receipt. In 1990, UPS improved its piracy technology by equipping its drivers with portable electronic computers called DIADs (Delivery Information Acquisition Devices). Each computer has a built-in bar code reader and a signature pad. When a delivery is made, the UPS driver scans the bar code on each package and then has the person receiving the delivery sign for the package. The bar code number and the handwritten signature are recorded inside the DIAD, and ultimately uploaded to the company’s databanks.

The push to make signatures available in electronic form came from UPS customers, Pat Steffen, a spokesperson for UPS, told me when I called the company to complain about the practices. Signatures are considered proof of delivery. Digitizing that proof allows UPS to manipulate it like any other digital data. The faxed proof-of-delivery certificates are sent automatically from UPS computers, she explained. It’s also possible for UPS customers to download tracking software and view the signatures directly on their personal computers.

Ironically, by making a person’s written signature widely available, UPS is helping to dilute the written signature’s very value. Once the signature is digitized, it’s easy to manipulate it further with a computer–for example, you can paste it at the bottom of a contract. UPS’s system is particularly vulnerable: any package can be tracked as long as you know the package’s airbill, and UPS issues its preprinted airbills in sequential order–for example, ‘0930 8164 904,’ ‘0930 8164 913,’ and ‘0930 8164 922.’ An attacker can easily learn a company’s UPS airbill, use that airbill to obtain a comprehensive list of every delivery recipient–and then make a copy of every recipient’s signature.

UPS understands the vulnerability, but it can’t address the problem very well. A note on the company’s web site says:

UPS authorizes you to use UPS tracking systems solely to track shipments tendered by or for you to UPS for delivery and for no other purpose. Any other use of UPS tracking systems and information is strictly prohibited.

But, realistically speaking, UPS can do little to prevent this kind of attack. ‘If someone wants to go out of their way to get package numbers, it can be done. If someone wants to go out of their way to do anything, I suppose that’s possible. It is not an easy thing to do,’ said Steffen. Guessing would be harder, of course, if UPS used longer airbill numbers and didn’t issue them in a predictable sequence.