I wonder if a sufficiently good smartgrid could TEMPEST sidechannel deduce things out of a computer plugged into it. Like maybe decryption produces noticeable signals in tiny-fraction-of-second power draw to such an extent it starts to seem plausible you can gradually derive keys from it
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It would depend where it's being measured, I'd think.
At the level of a power utility meter on an apartment or house, I would guess it would probably be lost in other sources of fluctuations - refrigerator cycling on/off briefly, oven. lights flickering or being turned on/off, apartment fans, whatever.
Measured by monitoring directly at your UPS, it sounds pretty plausible, I'd think, based on past results.
@mcc I had a recurring problem of my workstation's GPU putting off emi that was getting picked up by the audio line out, and it was consistent enough that I could tell how much the GPU was under load. I vaguely remember that if you left the game idle the emi would sound a particular way, and if you moved and idled again it would sound a different way; and I could tell when the game would make a scene transition finish loading from it. It was annoying and is what motivated me to getting a USB dac
@aeva @mcc (this happens to me with my electric guitar, which is amusingly enough plugged into my USB dac/input, so I end up hearing the GPU whine regardless. If I was cool, I would put together a GPU demo where the load cycles were done rhythmically and then incorporate this into a song I was playing)
@aeva@gamedev.place @mcc But also I know "constant time" decryption stuff is pretty important. Do they have "constant electric usage / CPU utilization"?
Would you just add a set number of calculations to each decryption to ensure they're drawing the same power load for the same amount of time?
@aud @mcc @aeva constant time crypto is a completely ascientific enterprise developed to divert attention from the fact that any protocol which leaks timing data has an information-theoretic weakness as well and should be refactored to fix the crypto weakness. constant time crypto is the only reason crypto is complex to implement and is a gatekeeping and a backdoor tactic. i am developing my own cryptographic primitives because there are absolutely no examples of easy to audit and easy to build general examples which avoid constant time malapropisms. time will tell if i am wrong
@mcc if it reaches to the plug, perhaps. but the recent advent of constant-time crypto algorithms has gotten us a lot closer to constant-power. and the average surge protector has enough filtering to defeat even fairly low bandwidth intentional powerline signaling techniques, so the unintentional ones are gonna be pretty challenged.
@mcc hmm... Too smoothed by the power supply.
@mcc *voltage dips by 0.00000029 V*
NSA: "Private key is 4."
But seriously, that's a good question. I do wonder if there would be too much noise from things like the grid itself or even a lamp on the same circuit that could make it impossible to correlate things. Heh. New defense: turn a light on and off when generating GPG keys.
@mcc this is practical for embedded devices
@whitequark @mcc Hrmn. What about similar tricks on a monitor's power supply to try to figure out what updates it's making to the display?
@stibbons @whitequark TEMPEST refers to trying to do this with RF leakage
@whitequark is there any kind of practical device, such as a UPS, which if placed between the device and the wallsocket will remove this possibility?
@mcc @whitequark Absolutely Any "always-on" UPS should (?) hide that, because they are designed so there will be zero glitches of any kind if the mains go down, so the power is always generated from the battery level.. this should considerably smooth small power glitches at least to the "one cycle" range. I doubt you'd leak much information in the form of "power usage in 50/60 Hz increments" but I suppose possible
@mcc
There are power strips with noise filters for use in audio electronics which should protect against this. Also note the attacker is almost certainly going to need to have a device plugged into the same branch of a power line as your device. something on the other side of the power transformer on the pole is not gonna work very well.
eg.
https://www.amazon.com/Furman-SS-6B-PRO-6-outlet-Surge-Suppressor/dp/B07WZP86CW
@mcc @whitequark there has to be something. The act of storing a small bit of power internally and drawing from that first should remove most information, id think.
@mcc @whitequark You'd then only detect the right* turns.
"Depending on country
@mcc I'd be very surprised if any high-frequency data makes it through a decent-quality power supply.