IT security policy “research”

“Researchers find way to steal encrypted data,” screams this article in the New York Times.

Oh do they? But come… on…, what is this ridiculous demonstration? Okay, okay, it’s the IT Policy School over there, let’s cut them some slack. What they’ve come up with is a way to read seated DRAM under OS lock without specialized hardware, and if they said that, it would be fine.

While I don’t care for their pseudo-slick presentation and shameless self-promotion (with a “blog”?), it is still a curious piece of work. Its unfortunate and regurgitated untechnicality leaves questions, though. DRAM is refreshed in tens of milliseconds, and since DRAM manufacturers are always trying to cut power consumption, I’m going to assume this rate is necessary to ensure reliable read out. There is a 3-order magnitude difference between that and the seconds to minutes reported that DRAM can be without power and still be read, during which time exponential charge decay takes place. Something else has to be going on, no? It just isn’t entirely clear that when the computer is turned off momentarily, on-board capacitors or even on-module capacitors aren’t discharging for long enough to residually power the refresh circuitry [*]. On the other hand, they claim they can remove the RAM completely and (with the help of liquid nitrogen) halt for an hour without power. I have some doubts as they dance around this issue.

As for real implication for security, there isn’t much, if only because this kind of breach isn’t fundamental. We already know that once indefinite hardware access to a running machine is first obtained (a practical requirement for this attack), there are always ways to compromise it. That’s how the Xbox was cracked — I’m talking about in-parallel probes on pins and traces, which can be just as well applied to the scenario here. Unless there are self-destructive mechanisms or other fundamental barriers to hardware access, we are just dealing with a matter of how high is the effort threshold. To fix it, encryption keys should not be stored in RAM in a detectable way, and any TPM modules that are currently being designed should have additional hardware security measures. That’s not hard to do, but in the meantime, let’s sit back and watch an uptick in the cracking of existing software and DRM protection schemes, as protected areas of RAM are opened up to easy hacking — a far more likely and practical fallout.

[*] I just read their full technical documentation, and they seem a little sloppy. They measure (and plot) total module read out error rate, but then fit a curve to it that they justify with MOSFET charge decay characteristics. Isn’t that right? Well, no: error rate should exhibit the typical digitizing water-fall effect of the comparator circuit.

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