Cryptographic Postage Indicia

We apply cryptographic techniques to the problem of fraud in metered mail. We describe a mail system that combines off-the-shelf barcode technology, tamper-proof devices, and cryptography in a fully-integrated secure franking system. This system provides protection against: 1. Tampering with postage meters to fraudulently obtain extra postage; 2. Forging and copying of stamps; 3. Unauthorized use of postage meters; and 4. Stolen postage meters. We provide detailed justification for our design, and discuss important tradeoffs involving scanning strategies, encryption technology and 2-D barcode technology. The US Postal Service’ recent Information Based Indicia Program (IBIP) [15] announcement adopted the principal design features of our model. 1 Motivation The US Postal Service1 handles over 165 billion pieces of mail each year through almost 40,000 autonomous post office facilities. Much of this mail is metered, which means that the mail does not have an ordinary stamp attached to it. Instead, a postage meter prints a special mark (called a postal indicia) on the mail. Fraud is a serious problem for the US Postal Service: The US Postal Service recently calculated that meter fraud cheats the agency out of substantially more than $100 million each year [4]. There are over 82,000 postage meters in the US that are currently reported as lost or stolen [14]. The US Postal Service is prosecuting two cases in New York and Boston; each involves more than $4 million dollars in postage meter fraud [10]. To address these problems, we propose a new system for printing postage indicia with cryptographic information. This system allows a PC or workstation with a laser printer and a tamper-proof device to produce unforgeable postage indicia. This paper describes that design. The design of cryptographic postage indicia is an interesting exercise in security engineering. The US Postal Service’s recent Information Based Indicia Program (IBIP) [15] adopts the principal design features of our model.