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Of course, this book is concerned about embedded systems that are involved in some security-
critical function, and some embedded systems lack security requirements altogether. This
book generally does not concern itself with a standalone, battery-powered thermostat run by an
8-bit microcontroller and a few kilobytes of software programmed in assembly code. The
largest security challenge in embedded systems lies in network-connected, sophisticated
electronic products that are managed by an embedded operating system running significant
software applications written in high-level programming languages such as C, Cþþ, Ada,
and Java.
1.3 Embedded Security Trends
The MP944, what many consider to be the world’s first microprocessor, ran the flight control
system aboard the U.S. Navy’s F-14 Tomcat fighter jet and began what has been more than 40
years of advancement in embedded systems technology. Depending on the particular analyst
asked, embedded computers account for 94% to 98% of the world’s computers. Practically every
major multinational corporationdfirms such as Lockheed Martin, Exxon, General Motors,
Hewlett Packard, and Johnson & Johnsondbuilds and depends on embedded systems within its
most important products. And, of course, the average consumer depends on the embedded
applications within aircraft, automobiles, games, medical equipment, and so on, constantly.
At the same time, software and hardware complexity, network connectivity, and malicious attack
threat continue to grow in embedded systems, which are increasingly relied upon for consumer
safety and security. The smart griddwith its smart appliances and sensors, smart meters, and
network gateways (all embedded systems)dis a good example, but only one of many. The
complex set of embedded systems and networks in a smart grid is shown in Figure 1.3.
1.3.1 Embedded Systems Complexity
One of the first embedded systems within an automobile was the 1978 Cadillac Seville’s trip
computer, run by a Motorola 6802 microprocessor with 128 bytes of RAM and two kilobytes of
ROM. The printed source code could not have occupied more than a handful of pages.
In contrast, even the lowest-end automobile today contains at least a dozen microprocessors;
the highest-end cars are estimated to contain approximately 100 microprocessors. With
infotainment systems running sophisticated operating systems such as Microsoft Windows and
Linux, the total embedded software content can easily exceed 100 million lines of code. The
F-35 Joint Strike Fighter’s avionics is estimated to host approximately 6 million lines of
code, driven by fly-by-wire controls, complex situational-awareness capabilities, sensor
processing, and high-resolution graphical displays for the pilot. Enterprise network switches
and routers routinely contain millions of lines of code for network protocol processing,
management and configuration, anti-virus rate limiting, and access controls.
4 Chapter 1