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Roving Transponder Method for Securely Programming a Distributed Collection of Changeable Units Disclosure Number: IPCOM000024642D
Original Publication Date: 2004-Apr-02
Included in the Prior Art Database: 2004-Apr-02
Document File: 7 page(s) / 252K

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This invention provides improved methods for securely loading changeable data into multiple ones of a physically distributed collection of programmable units. The units can be signs such as those used to convey speed or hazard warnings on the roadside; vending machines; billboards, and the like. The loading can be done securely by an authorized authority. The units can have wireless transponders capable of transmitting their identity to a roving transponder. The roving transponder can be deployed on a vehicle equipped with a database of units, their identities, locations, and authorized content. A cryptographic handshake or digital signature can be used to ensure that only authorized data is stored in the units. In addition to providing its message visually to passersby, the unit may be equipped with the ability to transmit its message electronically. When so equipped, the unit may become a control point of local processes such as a speed camera on the roadside near the unit.

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Roving Transponder Method for Securely Programming a Distributed Collection of Changeable Units

This invention is described with reference to a preferred embodiment involving programmable road signs. See [1] for examples of such signs. However, it can also be used for programming other types of changeable units such as vending machines. It is particularly suitable for any large collection of geographically distributed changeable units equipped with short-range wireless transponders, that occasionally need to be supplied with new data by an authority. "Unit" as used herein refers generically to some distinct type of changeable unit.

Each unit (see Fig. 1) has a unique identifier. The identifier could be its GPS coordinates, latitude/longitude with sufficient precision to distinguish closely-spaced units, a serially-incremented number qualified by an identifier for a registration authority such as a state highway department, a date/time first put into service, or fractional milepost number/highway number. The identifiers don't matter so long as they are reasonably short and unique across a defined geography. The identifiers are used to index a database of information about each unit. The database entry for each unit includes the unit's GPS location and a message that the unit should display (such as SPEED LIMIT CARS 65 MPH, TRUCKS 55 MPH, or CONSTRUCTION ZONE 25 MPH).

It would be desirable, but is not currently feasible, to vary the message displayed on many signs. For example a fixed roadside sign that always indicates a 75 MPH day-time speed limit and a 65 MPH night time speed limit could be replaced with a variable sign displaying "75 MPH" during daylight hours and "65 MPH" at night, controlled by a light sensor. A sign that indicates a lower speed when construction personnel are present could automatically revert to the normal speed on weekend when construction work pauses, based on an internal time-of-day clock. A legislated speed limit change on a roadway today requires physical redeployment of thousands of signs, an expensive process that is personnel- and resource-intensive, and slow. Using this invention, the speed limit can be changed on hundreds or thousands of sign units in the time it takes for the official vehicle to drive around transmitting the update.

It is possible, but expensive, to equip each unit with a cellular telephony transponder, allowing all units to be programmed wirelessly and nearly instantly from a central location. Instead, costs can be reduced greatly by equipping the units with a short-range passive or active wireless technology such as RFID and programming them from a roving vehicle that transmits the data wirelessly when it comes in range. In this application, instant simultaneous updates are neither necessary nor cost-effective.

The unit is equipped with public key cryptography capability, and the X.509 certificate of the authority (or authorities) permitted to change the unit is preloaded into t...