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Balancing cost vs. security for embedded design

Posted: 16 Feb 2006 ?? ?Print Version ?Bookmark and Share

Keywords:bernard cole? ee times? embedded security? security cost? wireless security?

In mainstream computing, it has been accepted that ubiquitous connectivity comes at the cost of constant vigilance and continued investment in security. However, users and developers of the embedded MCUs that populate industrial, building and home environments are only buying into the idea that security is a necessary long-term cost of doing business, with benefits that offset the expense of development, installation and long-term maintenance.

Wireless connectivity is changing minds in the form of specifications such as zigbee and a variety of wlan implementations. "The extraordinary cost reductions and flexibility that wireless brings to many MCU-based applications is convincing embedded-MCU developers that there is enough benefit to offset both the initial and continuing costs of security technology," said Mukesh Lula, president of TeamF1 Inc.

"Beyond the huge cost savings incurred by eliminating wires are the continuing costs in maintenance that will be eliminated," Lula said. That gives added flexibility to "the manufacturer who wants to reorganize the factory floor, add new systems and eliminate others. Having no wires to connect and disconnect will make the factory floor a much more dynamic environment." But wireless will also make the embedded-control environment a much leakier one, leaving telltale RF signals that make networks more susceptible to snooping, hacking and sabotage.

According to Jacko Wilbrink, ARM-based MCU marketing manager at Atmel Corp., such vulnerabilities quickly became apparent to providers and users of the supervisory control and data-acquisition network systems used in many manufacturing facilities, power plants, chemical and fuel distribution centers.

As manufacturing and building automation systems become roboticized and sensorized, the ability to connect to MCU-controlled equipment and gather information will be a compelling argument for integrating such gear into security frameworks. "Once a Zigbee- or Wi-Fi-connected network of sensors in a plant is connected to the enterprise for the purpose of information collection, security issues become more likely," said Rich Swindlehurst, manager of the Security Technology Center at Freescale Semiconductor Inc. "Industrial espionage still occurs and breaking into such connected enterprises to extract information has considerable benefit."

Among systems vendors, OEMs and VARs, the focus is on the positive aspects of wireless networks; little effort has been made to sell security. But "there are a lot of security and privacy issues, even in the home environment," said Lula of TeamF1. "With a wired system, unless someone actually has access to the wires and physical nodes, security breaches are unlikely. But with wireless, you are naked to the world. Anyone driving by with the right equipment can listen in on everything."

Naked environment
"The big question is how quickly embedded designers will implement all the necessary security in such a connected and naked environment," said Fani Duvenbarge, rfPIC product manager at Microchip Corp. "As serious as the potential security problems could be, MCU application developers are extraordinarily cost-sensitive, power-sensitive and under severe constraints to service the real-time and deterministic requirements of their designs."

Aware that security will quickly move to the top of the agenda among developers and end-users as wireless connectivity becomes ubiquitous, most major providers of MCU silicon are actively involved in industry groups, such as Zigbee and the Trusted Computing Group, to implement the appropriate security standards.

Meanwhile, MCU vendors such as Atmel, Freescale, Microchip Technology, STMicroelectronics and Texas Instruments are providing software, tool support and, in some cases, specialized silicon with a wide range of encryption protocols built-in, but the emphasis varies from vendor to vendor.

Most current MCU security solutions are adaptations of standards, architectures and methods found useful in mobile platforms, desktops, laptops and servers, said Mitch Blaser, product manager at security specialist Certicom Corp. These include symmetric algorithms (e.g. DES, AES and double DES) for encrypting messages between devices for which there is an already established degree of trust, and asymmetric algorithms (e.g. RSA and elliptic-curve digital signatures) for applications where it is necessary to have some mechanism for validating identity and trustworthiness.

"We start with standards and algorithms that have worked in other segments of computing and communications, and apply them where appropriate in the embedded space," said Swindlehurst of Freescale. "With few exceptions, standards and specifications developed for a much different computing space are working well so far in the deeply embedded environment where MCUs operate."

But Eric Uner, who works on security issues related to mobile and embedded devices at Motorola Laboratories, is concerned that there is far too much focus on encryption algorithms and not enough on developing a systems-oriented approach to device-level security. "More than other segments of connected computing, embedded MCUs and the sensors and control elements to which they are linked are sensitive to security attacks that do not require trustedness or access to information that has been encrypted," he said.

Uner said he does not rule out the possibility of denial-of-service attacks that would "overwhelm local controllers tied to sensors with spurious input data. And in a wirelessly connected MCU environment, there are at least half a dozen ways to overwhelm a network of MCUs and prevent them not only from communicating, but from doing their control functions as well."

In a wireless environment, an intruder doesn't need to fool a system into authorizing access or break open an encrypted packet to extract useful information. "If you know that a manufacturing facility builds particular items and you want to know when and how much is being produced and on what schedule," said Uner, "you just have to watch the network activitywhen it peaks, when it doesn't, where it is occurringto have information that a competitor would find useful."

Thus, Uner said embedded developers using MCUs must fundamentally rethink embedded security in three areasthe algorithms used to provide security, the proper framework within which to think about the problem and the most appropriate MCU hardware and software.

For its most recent ARM-based MCU design, said Atmel's Warren, engineers discovered that with Zigbee, "doing symmetric DES and AES encryption in software often requires more than 90 percent of an MCU's resources. That has forced us to rethink the way data is moved to and from on-chip peripherals and memory."

- Bernard Cole
EE Times

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