FPGA Bitstream Security Broken

NumberField writes "Researchers in Germany released a pair of papers documenting severe power analysis vulnerabilities in the bitstream encryption of multiple Xilinx FPGAs. The problem exposes products using FPGAs to cloning, hardware Trojan insertion, and reverse engineering. Unfortunately, there is no easy downloadable fix, as hardware changes are required. These papers are also a reminder that differential power analysis (DPA) remains a potent threat to unprotected hardware devices. On the FPGA front, only Actel seems to be tackling the DPA issue so far, although their FPGAs are much smaller than Xilinx's."

Comments

Good or bad?

[Hatta]

Is this the good kind of security breach, which enables end users to do new things with their FPGAs? Or the bad kind, that enables attackers to do malicious things with others FPGAs? Or both?

Re:Good or bad?

[Anonymous Coward]

If the encryption is cracked it can expose the core to reverse engineering as well as injecting malicious code. If the bitstream contains a soft processor and sw image it could really get interesting as it opens up another vector for getting malicious software onto the device in question.

Re:Good or bad?

[Andy Dodd]

There's nothing about the Xilinx bitstream encryption that prevents you from loading in an unencrypted bitstream, or a new bitstream with a new key.

Unfortunately it means that it's easier to compromise/clone/tamper with FPGA designs. FPGA cloning/tampering has been a big problem for Cisco as I understand it (counterfeit Cisco products).

Re:Good or bad?

[Animats]

Is this the good kind of security breach, which enables end users to do new things with their FPGAs? Or the bad kind, that enables attackers to do malicious things with others FPGAs? Or both?

This attack is only useful when an FPGA is programmed by a third-party manufacturer using a canned encrypted bitstream provided by someone else. This is the case for many products nominally made by US, Japanese, or Taiwanese firms but actually built in China. The attack allows someone with access to the encrypted bitstream to recover the unencrypted bitstream, from which they can potentially reverse-engineer the device and make changes.

An end user, who has only the programmed FPGA, can't do anything with this attack.

For background, here's a short note on where this technology is used.

Re:Good or bad?

[harrkev]

Also, if you SELL products with FPGAs in them, it makes it harder to make a profit if somebody decides to reverse-engineer your stuff. Really, all this is good for is cracking into a design that somebody else made. Once you GET the actual bitstream, there are really two things that you can do with it...

1) Make copies of the FPGA. Boards are not that hard to reverse-engineer, so you could copy somebody else's design completely.

2) Reverse engineer the code. However, you will NOT have anything that would help you do this, like net names or hierarchies. This will make actual reverse-engineering in order to change something or learn something very challenging.

This doe NOT make FPGAs any more useful, since you can easily download free development software from every FPGA vendor and put whatever you want on there. Really, the only thing that you CAN'T do with the free software is stuff related to licensed IP (processor cores, various controllers for things like Ethernet, SATA, etc.). While you COULD pull that out of an encrypted bitstream, using it without any sort of documentation or the configuration wizards would be very challenging and, 9 times out of 10, it is just easier to pony up the money to license the cores in the first place.

Re:Alright, someone help

[Anonymous Coward]

As transistors switch they create little glitches in the power supply, or rather they consume a little more or less current than at the previous steady state (where steady state may be nanoseconds long). By correctly interpreting the changes in current consumption the encryption key can be read.

For the car analogy (this is slashdot after all) think of it as monitoring fuel flow to extrapolate acceleration, speed and distance.

Re:Alright, someone help

[Anonymous Coward]

An FPGA is sort of like a PROM except that instead of memory circuits you program logic circuits into it.

If this hack allows people to reverse-engineer the chip, they can basically dump its logic diagram, which means that they could copy it. As I understand it, it's normally pretty hard to reverse-engineer a microchip, so this is a pretty significant breakthrough.

Re:they would have to add additional circuitry...

[Anonymous Coward]

There is only so much you can do. We put a fair amount of power supply filtering around FPGAs because of the switching noise, but the cost in board space and materials to make the switching undetectable would be astronomical. As HW engineers we're always asked to cram a little more in that space, and "do you really need that many capacitors?"

The company I work for (and the reason I'm posting anonymously) uses a bunch of FPGAs per board with man-years of code invested into them, and we usually use Xilinx parts. It's relatively trivial to get the bitstreams from our systems which hasn't bothered us since they're encrypted (or I guess they used to be).

Re:DPA protection is patented...

[bws111]

Yet another idiot who doesn't understand the simple fact that the 'obvious' test is applied BEFORE the patent is public. Of course it is 'obvious' AFTER the patent is public. If you asked 100 people working in the field how to "defend against DPA and other side-channel attacks" BEFORE the patent (or anything using the patent, or any papers based on the patent, etc) was public, what percentage of them would have come up with the EXACT SAME WAY (not 'general concepts', the exact methods used) that CR did? It had better be very close to 100% if you are going to claim 'obvious'. If you ask these same 100 people AFTER the patent is public, 99 of them will claim that the CR method is 'obvious'.

Re:General concepts

[kbonin]

You miss the point - the researchers discovered an application of the laws of physics to cryptanalysis. Cool, interesting, but not inherently patentable. Then they patented every way to fix that problem, many of which would be obvious to someone skilled in the art.

If I discover that 1+2 = 3, I cannot patent that equation. If I discover an application of that equation to a physical problem, the intent of the framers in patent law was that only a non obvious application may be patented. The fact that they discovered the problem doesn't (at least by law) eliminate or nullify the PHOSITA requirement.

The researchers found a hard to find problem, then patented the obvious solutions to that problem.

This is one of the problem with patents in general - patents are being issued where the person "skilled in the art", i.e. someone who has the same degree of specialization, would have developed the same solution, and the USPTO no longer makes a reasonable effort to prevent that.