Backdoor in chip used by military: Blame software, not China
- By Kevin McCaney
- May 30, 2012
The recent discovery by British researchers of an intentionally placed backdoor in U.S. chips used in defense and industrial systems set off a brief frenzy of finger-pointing toward China, with claims that Chinese manufacturers were prepping the chips for a series of Stuxnet-type attacks on U.S. systems.
Not quite. There has been plenty of evidence in recent years that China has conducted attacks and/or espionage via the Internet, but in this case, it’s not involved. And the backdoor in the chip apparently wasn’t malevolent, but simply the result of software complexity.
Sergei Skorobogatov, a Ph.D. candidate at the University of Cambridge, recently released a draft paper on research into silicon chips that was prompted by intelligence community concerns that the chips could be exploited.
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As part of the research, he discovered a backdoor built into the silicon in Microsemi/Actel ProASIC3 chips. Using a technique called Pipeline Emission Analysis, he and fellow researchers were able to extract the key to the backdoor, which would allow an attacker to disable the chip’s security, reprogram it or permanently damage it.
The chips are used in military and industrial systems such as nuclear power plants, and “this backdoor access could be turned into an advanced Stuxnet weapon to attack potentially millions of systems," Skorobogatov wrote.
And because the chips are manufactured in China for the California-based Actel, a division of Microsemi, suspicion quickly fell to the Chinese, especially after Skorobagatov’s paper began circulating on the Web and a number of news outlets ran stories linking China to the chips.
But those claims were quickly disputed, even by Skorobogatov, who told ZDNet Australia that Actel, not a Chinese manufacturer, inserted the backdoor.
"The claims about [the] Chinese being involved, was made up by someone who originally made the post at Reddit," he told ZDNet. “It is as though people have put two and two together and made four or five or six, depending on what their agenda is.”
He pointed out that their papers makes no direct claims about China’s involvement — although they note that the chips are manufactured there and emphasize the connection — and said he expects that other chips will have similar backdoors.
In fact, such backdoors are common, according to Errata Security’s Robert David Graham, whose blog post was perhaps the first to dispute the claims. Twenty percent of home routers and 50 percent of industrial control computers have backdoors, for example. However, “the cause of these backdoors isn't malicious, but a byproduct of software complexity.”
Chips embedded in systems have to be debugged before they are shipped, which requires the backdoor, Graham wrote. And because it costs too much to disable the debug feature — each change in chip design can cost millions of dollars — the chips tend to be shipped with the debugging interface enabled. That makes them vulnerable to hacking, although a hacker would have to have physical access to the chip, he wrote.
The chips can be protected with a key to the backdoor known only to the manufacturer, Graham wrote, which the chip had but which Skorobogatov was able to extract.
A chip such as the ProASIC3, a field-programmable gate array, also can be protected with 128-bit Advanced Encryption Standard encryption, since it exists as a file on the drive within its system, he said.
The discovery of sophisticated malware such as Stuxnet, which disrupted uranium processing in Iran, and the recently discovered Flame, a spyware program attacking targets in Iran and elsewhere, have raised fears about attacks on industrial systems. And China has been no angel when it comes to cyber shenanigans.
But in this case, the backdoor does not appear to have been placed there as part of a nefarious plot. Although the researchers did reveal yet another potential vulnerability — and provided another demonstration of how fast news, accurate or not, travels on the Web.
Kevin McCaney is a former editor of Defense Systems and GCN.