Sidebar 1-1: Protecting Software in Automobile Control Systems
The amount of software installed in an automobile grows larger from year to year. Most cars, especially more expensive ones, use dozens of microcontrollers to provide a variety of features to entice buyers. There is enough variation in microcontroller range and function that the Society of Automotive Engineers (Warrendale, Pennsylvania) has set standards for the U.S. automotive industry's software. Software in the microcontrollers ranges through three classes:
low speed (class Aless than 10 kb per second) for convenience features, such as radios
medium speed (class B10 to 125 kb per second) for the general transfer of information, such as that related to emissions, speed, or instrumentation
high speed (class Cmore than 125 kb per second) for real-time control, such as the power train or a brake-by-wire system
These digital cars use software to control individual subsystems, and then more software to connect the systems in a network [WHI01].
However, the engineers designing and implementing this software see no reason to protect it from hackers. Whitehorn-Umphres reports that, from the engineers' point of view, the software is too complicated to be understood by a hacker. "And even if they could [understand it], they wouldn't want to."
Whitehorn-Umphres points out a major difference in thinking between hardware designers and software designers. "As hardware engineers, they assumed that, perhaps aside from bolt-on aftermarket parts, everything else is and should be a black box." But software folks have a different take: "As a software designer, I assume that all digital technologies are fair game for being played with. . . . it takes a special kind of personality to look at a software-enabled device and see the potential for manipulation and changea hacker personality."
He points out that hot-rodders and auto enthusiasts have a long history of tinkering and tailoring to make specialized changes to mass-produced cars. And the unprotected software beckons them to continue the tradition. For instance, there are reports of recalibrating the speedometer of two types of Japanese motorcycles to fool the bike about how fast it is really going (and thereby enabling faster-than-legal speeds). Whitehorn -Umphres speculates that soon you will be able to "download new ignition mappings from your PC. The next step will be to port the PC software to handheld computers so as to make on-the-road modifications that much easier."