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Mutual Information Analysis

Benedikt Gierlichs, Lejla Batina, Pim Tuyls, Bart Preneel,

CHES 2008

Abstract:

We propose a generic information-theoretic distinguisher for differential side-channel analysis. Our model of side-channel leakage is a refinement of the one given by Standaert et al. An embedded device containing a secret key is modeled as a black box with a leakage function whose output is captured by an adversary through the noisy measurement of a physical observable. Although quite general, the model and the distinguisher are practical and allow us to develop a new differential side-channel attack. More precisely, we build a distinguisher that uses the value of the Mutual Information between the observed measurements and a hypothetical leakage to rank key guesses. The attack is effective without any knowledge about the particular dependencies between measurements and leakage as well as between leakage and processed data, which makes it a universal tool. Our approach is confirmed by results of power analysis experiments. We demonstrate that the model and the attack work effectively in an attack scenario against DPA-resistant logic.

Paper Available At:

http://springerlink.com/content/t274j41273077884/?p=a759fb749b09468588...

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Review by mrcatman for Rating: We have a very siplme setup, with 90% of our use being watching cable company s DVR on the TV. PROS:- Very easy to set 8/8/2012 4:26:21 PM

- Review by mrcatman for Rating: We have a very siplme setup, with 90% of our use being watching cable company s DVR on the TV. PROS:- Very easy to set up- Small speakers (i.e., wife-friendly size/dimensions)- Wired internet worked quickly/easily- LG updates downloaded quickly, installed easily (wired internet)- Two HDMI inputs on the device is nice- Support for internet streaming is nice (YouTube, Netflix, etc.)- iPod dock is nice (charges too)CONS:- Sound quality is horrible- Popping sounds changing LG s input- Popping sounds using DVR (even with each channel change)- Awful reverse communication through HDMI to DVRLet me give some more details on the CONS above.Sound QualityThe sound from these speakers is best described as extremely tinny. All dialogue sounded nasally, like the actors had a cold. It s not a subtle thing. It s very noticeable, omnipresent and completely distracting. We tried to adjust the speaker volumes, but the sound quality did not improve. The subwoofer had no sweet spot. It seemed to either produce almost non-existent low end or a dull woofing that was obviously too much and nothing in between. Our previous all-in-one home theater was nothing special, and is very old; and it never sounded this bad. Even our TV s built-in speaker (also nothing special) sounds significantly better than the LG. To us, the poor sound quality of the LG was enough to outweigh any of the positives this box has.Popping Sounds Changing LG InputsWhen you change the LG inputs from anything to anything, you hear a popping sound in all speakers. It s not loud, but it s loud enough to hear it from the couch s normal TV-viewing position. The popping happens regardless of listening volume level and even with sound muted. It happens whether you change inputs from the face of the box or using the remote. It happens no matter what you had connected to the HDMI ports (or if those devices were powered off) and even with nothing connected in/out HDMI. We called LG support on this. We triple-checked speakers were correctly connected, that there were no power/speaker wire cable crossovers and did their normal troubleshooting steps (reset the box, download all current LG updates, etc.). The popping persists. I don t know if this is merely a defective unit or a problem with all their boxes, but it is a pretty annoying thing.Popping Sounds Using DVRThe same popping sound from above (changing LG inputs) also happens during normal operation of our cable company s DVR. Change the channel on live TV, it pops (every time!). Play a recorded show, it pops. Switch to On Demand, it pops. Our DVR is Time Warner s DCH3416. It was connected from the DVR s HDMI out to the LG s HDMI input. The LG s HDMI out was going to the TV s input. As basic as it gets. The popping happened whether the DVR was connected to LG s HDMI input #1 or #2. The popping happened with a second DVR box (we have two of them, same model). The popping happened even when no devices were connected to the other inputs. We don t hear the popping if we connect the DVR to the TV directly (and TV optical audio out to the LG input). So it s unlikely to be a defective DVR. Again, I don t know if this is a defective unit or a problem with all LGs.Reverse Communication through HDMII was under the impression that DVR (HDMI out) to LG (HDMI input) was a one-way communication. I.E., only video/audio would travel from the DVR to the LG, and nothing would travel through that same cable from the LG back to the DVR. However, strange as it may seem, the LG sends info back to the DVR. The net result is that the LG would change the DVRs settings and stop displaying the video/audio. You d get an on-screen message saying it could not display anything. In researching this more, we found the DVR had a user settings, where you can set the 4:3 Override mode. The factory default is 480i, which will display standard-definition programs in 480i (720 480), but will automatically change to 1080i (1920 1080) when watching high-definition programs. This switching between resolutions messes up the LG, which results in the error and shutting off the video/audio. So the easy solution was to set the 4:3 Override mode to Off, which will create a widescreen version of standard-definition programs (adding black bars on left/right of picture). The result is the the cable DVR box now STAYS on 1080i resolution no matter what kind of program you are watching. The LG likes this, and is able to display video/audio properly.Until you turn off the TV. When you turn off the TV (leaving the cable DVR box on, and the LG on), the LG resets the cable DVR box to 480i mode, and the LG no longer can display video/audio. That means that the TV sent info back along the HDMI cable to the LG (even though it s only connected from LG out to TV in), and the LG proceeded to send info back along the HDMI cable to the DVR (even though it s only connected from DVR out to LG in). It s the strangest thing we ve ever experienced.The net result is, every time you turn off the TV, the cable DVR box was unviewable the next time your turned on the TV. Obviously, this was completely unacceptable. After working with LG support, there was no solution. I don t know if this was a defective LG unit (vs. a problem with all their units) or a problem specifically with our DCH3416 model DVR (i.e., newer DVRs might not have this issue?). But since we have two DVRs (same model), and the same thing happened with both, I don t think it was a defective DVR unit.There was another setting in the DVR to change audio from pass through to something else, which fixed the popping sounds (only using DVR, it still popped changing LG inputs), but because the DVR kept resetting as described above, the popping would return each time the TV was shut off.SummaryEven if the popping sounds were not there, and the DVR was not resetting each time the TV was shut off, there still was the biggest issue of all the sound quality was very poor. That alone was enough reason to return it. I recommend getting a different product.Follow-Up:I returned the LHB535 and bought the lower-end LHB335 to see if was any better. It also had all of the same problems (popping, HDMI backtalk to the DVR which stopped picture working on next power on) and ADDED the new problem of the tea-pot sounding whistle out of the speakers as others have experienced. The whistle happened as soon as the LG was powered on, even with volume down and muted. It is just omnipresent.So it seems that the 335 model and 535 model have all the same issues. I still was unimpressed with the sound quality of the various sound field options (pcm movie II, etc.). The speakers of these LGs simply do not put out rich, well-rounded sound.Other Products We TriedWe also bought (and returned) the Sony HT-CT150 soundbar/sub HTIB. It has 3 HDMI inputs (no Blu-Ray, no streaming, no real surround) and had sound quality on par with the LG 335. We bought (and returned) the new Samsung HT-C6500 (the best sounding, WAY better than this product), which would have been perfect except it had lip sync issues. We bought (and returned) the new Sony E570 (no HDMI inputs, but very good sound) with the idea of using the TV as the HDMI hub, and running TV optical audio out to the Sony just for sound. This would have been the perfect solution, but our TV is old, and the optical out (which we learned too late) does not pass the HDMI audio along. We also bought (and returned) the new YHT-S400 soundbar/sub HTIB. It sounded on par (or slightly better) than the Sony HT-CT150, but was expensive for what it was.ConclusionAt the moment, all the HTIBs (1) in this price range, (2) with internal Blu-Ray and (3) with HDMI inputs have unacceptable issues (to us, at least) assuming you use the HTIB as the hub for all our incoming sources. I recommend you get a decent HDMI receiver and grab the $135 Panasonic BD65 (Blu-Ray with streaming).