[HN Gopher] Video: Power LED Attack [video]
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Video: Power LED Attack [video]
Author : DamnInteresting
Score : 65 points
Date : 2023-06-29 20:10 UTC (3 days ago)
(HTM) web link (www.youtube.com)
(TXT) w3m dump (www.youtube.com)
| breput wrote:
| This is solved by extending the constant time calculation
| principle to the CPU instruction level. Easier said than done,
| but probably only really necessary on HSMs or smart cards.
|
| On a side note, the Computerphile[0] YouTube channel has an
| endlessly fascinating variety of computer science, theory, and
| history videos. A related channel that is equally worth following
| is Numberphile[1].
|
| [0] https://www.youtube.com/@Computerphile/videos
|
| [1] https://www.youtube.com/@numberphile/videos
| lloydatkinson wrote:
| I'm fairly sure it is also solved by having a decoupling
| capacitor for the LED too...
| husam212 wrote:
| Best solutions are the simplest ones, and this is the right
| one! It's an electrical coupling issue so I think it should
| be fixed electrically.
| yonatan8070 wrote:
| I'm guessing a capacitor would help negate this issue but it
| won't be possible to entirely eliminate the issue
| properparity wrote:
| A capacitor is a few extra cents on the bom which is a no
| go for profit maximizing companies.
| mikelovenotwar wrote:
| Dyson batteries are a good example:
|
| Dyson vacuum batteries are designed to fail
|
| * Series battery cells in a battery pack inevitably
| become imbalanced. This is extremely common and why cell
| balancing was invented.
|
| * Dyson uses a very nice ISL94208 battery management IC
| that includes cell balancing. It only requires 6
| resistors that cost $0.00371 each, or 2.2 cents in total
| for six.
|
| * Dyson did not install these resistors. (They even
| designed the V6 board, PCB 61462, to support them. They
| just left them out.)
|
| * Rather than letting an unbalanced pack naturally result
| in lower usable capacity, when the cells go moderately
| (300mV) out of balance (by design, see step 3) Dyson
| programmed the battery to stop working...permanently. It
| will give you the 32 red blinks of death and will not
| charge or discharge again. It could not be fixed. Until
| now.
|
| https://github.com/tinfever/FU-Dyson-BMS
| tjoff wrote:
| That is not about saving cents tough.
| H8crilA wrote:
| No, it will completely eliminate it, if the capacitor is
| large enough. If you're super paranoid you can do the maths
| and compute how much does it cut off at such frequency
| ranges. It's likely to be a ridiculous value. And one does
| not have an infinite amplitude resolution in any
| measurement device.
|
| Also, you can just power the LED from a separate voltage
| regulator. Which is somewhat likely anyways, as the IC will
| probably want a lower voltage.
|
| (Don't get me wrong, it's cool stuff, but there's also a
| very easy solution.)
| dvwobuq wrote:
| It's a harder EE problem than you think. For example the
| Samsung Galaxy S8 was attacked by analyzing video footage
| of the power LED of Logitech Z120 USB speakers. Those
| were most certainly on a different power supply and the
| two were connected by a long wire.
|
| There are circuit level solutions but the solution is not
| a $0.01 MLCC.
|
| And once you solve the LED problem remember: The S8 was
| attacked by plugging in a peripheral to it's 5V USB
| supply. Imagine if the peripheral was instead a high
| speed ADC that just measured 5V USB directly...
| rolandog wrote:
| // TODO remove ductape; temp fix of https://ia.cr/2023/923
|
| Edit: Joking aside, capacitors and black tape are actual
| countermeasures: Fig. 15. A circuit that
| leaks information via its power LED (a). Counter-
| measures using a capacitor (b), an additional OPAMP (c),
| and an existing
|
| OPAMP (d).
|
| And: Consumer Side Methods. The attack
| can also be prevented by placing black tape over a
| device's power LED.
| jacquesm wrote:
| or just snipping it.
| TedDoesntTalk wrote:
| Or simply manufacturers not using LEDs to indicate
| activity.
| jacquesm wrote:
| They don't. The LEDs fluctuations are a by-product of
| power rail fluctuation and this in turn can be detected
| to discover some elements of the computations involved.
|
| It's pretty subtle. This isn't like a flashing harddrive
| LED, it is an LED that to all intents and purposes is
| burning steadily. Until you look at it in more detail and
| you realize that it isn't quite as steady as it should
| be.
| sokoloff wrote:
| This is not an _intentional_ indication of activity, but
| rather just of power.
| jahsome wrote:
| Comment: Neat. [comment]
| CyberDildonics wrote:
| I'm with you, this is a very bad title. It already links to
| youtube so video doesn't need to be there once, let alone
| twice.
| jahsome wrote:
| I just thought it was silly! I actually appreciate the
| clarity, I wish more posts had a "flair" indicating what
| hides behind the link.
| daly wrote:
| I seem to be missing something that makes this unlikely.
|
| Most chips have a capacitor across the power pins. That would
| tend to "integrate" the signal.
|
| Recent chips operate at sub-volt values but the LED is in the 2+
| volt range so they likely are on different rails of the power
| supply or have buck/boost circuits.
|
| Even trivial designs don't use full in-order processing so
| multiple ADDs might overlap a MULT. This ain't your father's
| first processor.
|
| The traces on the board, if not carefully designed, likely have
| reflection and ringing effects, especially at via points making
| the signal rather noisy.
|
| Processors are running in the nano/pico range but the led/camera
| likely can't reach that resolution.
|
| At these speeds the resistor-to-ground circuit on the LED would
| have capactive and inductive effects that would be hard to model
| and need to be pre-measured.
|
| If it is a near-field (touch card) key then there are a lot of
| other noise sources including other chips and circuit trace
| induced voltages.
|
| Cryptographic coprocessors in Verilog/VHDL are available as open
| source or vendor IP. They won't leak.
|
| I could construct a "bench level test" that MIGHT be able to
| detect the computation but I'd need a really good oscilloscope on
| a well engineered circuit board knowing the exact specs of the
| processor and knowledge of the algorithm used.
|
| Oh, and as mentioned, nobody who knows anything about crypto
| already knows and protects against timing/power attacks.
| dvwobuq wrote:
| > I could construct a "bench level test" that MIGHT be able to
| detect the computation
|
| No need. The author of the original paper already did that for
| you. https://eprint.iacr.org/2023/923
|
| "We demonstrate the application of video-based cryptanalysis by
| performing two side-channel cryptanalytic timing attacks and
| recover: (1) a 256- bit ECDSA key from a smart card by
| analyzing video footage of the power LED of a smart card reader
| via a hijacked Internet-connected security camera located 16
| meters away from the smart card reader, and (2) a 378-bit SIKE
| key from a Samsung Galaxy S8 by analyzing video footage of the
| power LED of Logitech Z120 USB speakers that were connected to
| the same USB hub (that was used to charge the Galaxy S8) via an
| iPhone 13 Pro Max."
|
| To all the EEs out there. PSRR and power supply cross talk is a
| thing...
| hulitu wrote:
| > To all the EEs out there. PSRR and power supply cross talk
| is a thing...
|
| Damn, i have to cover my hdd led on the computer case so the
| neighbours do not see the pornos that i watch. /s
| tjoff wrote:
| > _Processors are running in the nano /pico range but the
| led/camera likely can't reach that resolution._
|
| You don't need a lot of precision to get enough hints of a key
| to be able to brute-force the rest.
|
| > _Oh, and as mentioned, nobody who knows anything about crypto
| already knows and protects against timing /power attacks._
|
| Sounds like this could never be a problem then! But it is.
| rolandog wrote:
| Ooh, I never considered the rolling shutter effect.
|
| That's amazing. The paper is called "Video-Based Cryptanalysis:
| Extracting Cryptographic Keys from Video Footage of a Device's
| Power LED" [0].
|
| Edit: Also, worth viewing the video [1] on the author's post [2].
|
| [0] https://eprint.iacr.org/2023/923
|
| [1] https://youtu.be/ITqBKRZvS3Y
|
| [2] https://www.nassiben.com/video-based-crypta
| fisian wrote:
| Rolling shutter is quite nice and used in different scenarios
| to increase framerate.
|
| For example to extract sound from just a camera [1].
|
| Additionally, while not directly related to the rolling shutter
| effect [2] uses a technique to increase the framerate of the
| Raspi Camera by 10x or more, but reducing image resolution.
|
| [1] https://people.csail.mit.edu/mrub/VisualMic/
|
| [2] https://github.com/Hermann-SW/fork-raspiraw
| redroyal wrote:
| Thrilled that this guy read a paper then explained it to us all
| very slowly using the words actually and basically. He appears to
| have had nothing to do with authoring of the paper and was unable
| to show a demo of the technique. Great that he thinks it's
| interesting though and the advice to not leak the secret key
| accidentally is priceless. We're all back to the drawing board
| now
| scyzoryk_xyz wrote:
| "Be kind. Don't be snarky. Converse curiously; don't cross-
| examine. Edit out swipes." [1]
|
| I actually highly recommend the rest of computerphile YT
| channel - basically, it would seem that most of these guys
| actually teach computer stuff for a living.
|
| [1] https://news.ycombinator.com/newsguidelines.html
| redroyal wrote:
| alright that was mean. but I'm winning points, so I could
| make a very sound argument that even though contradicting the
| guidelines I was incentivized by design to be mean. In a way,
| I'm an innocent victim of unspoken policy
| squarefoot wrote:
| Ironically, using an old tech incandescent lamp in place of the
| LED would make the detection impossible, the reason being that
| incandescent lamps are way slower to turn on and off than LEDs,
| therefore it would work as a low pass filter just like putting a
| capacitor in parallel to the LED, which makes a RC filter paired
| with the series resistor preceding it.
|
| Of course one could still use LEDs of which they have gained
| control for exfiltrating information, whether LEDs have a
| capacitor in parallel or not. If there is a capacitor and the LED
| can't be turned on and off effectively at say more than 5Hz, one
| could just use 1Hz pulses and, given enough time, transmit the
| information anyway.
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(page generated 2023-07-02 23:02 UTC)