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by megous 844 days ago
You don't just sniff a 48Gbit/s protocol as a random hacker. That's not what happens in the real world. A real-time scope that could do that is in the $1mil dollar range.

At best a random hacker will reverse engineer the binary driver enough to make something work in some capacity.
4 comments
CuriousCosmic 841 days ago
Yes you actually can. It's known that HDMI is TMDS and that the fastest frequency on any given pair is 680MHz and there are a total of 13 data pins (4 pairs + i2c + CEC pin + hot plug detect pin + reserved pin for some special features). A digital logic analyser that can sample at that rate over all 13 pins is going to cost less than a grand. If you stub in some hardware to convert the differential pairs back to a single hi/low signal and drop the optional features of the reserved pin, you can cut that down to 8 signals (or less if your analyzer has dedicated clock signal pins). A DSLogic U3Pro16 is 299usd and can sample 8 signals at 1GHz in buffer mode or 3 pins at 1GHz indefinitely in streaming mode.

If you know roughly what you are looking for, you can set triggers to start sampling when the event you care about starts, that's more than enough to be able to reverse engineer even the most intensive of the existing HDMI spec.

Given that a lot of these graphics cards cost substantially more than 300usd, it's not unreasonable to expect a logic analyzer capable of digesting HDMI to be within their price range.

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ZiiS 844 days ago
A lot of those $1mil dollar scopes run Linux and connect to fast, high resolution displays; some of them are made by companies not always in love with US licensing.
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fps_doug 844 days ago
Sure, but this is a hypothetical scenario, focusing on the legal aspects.
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megous 844 days ago
Legal aspects of something that can never happen? Why?

Try legal aspects of reverse engineering a binary driver. That's more realistic.

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iforgotpassword 844 days ago
But the question is not whether it's legal to reverse engineer a binary. The question is whether someone with no affiliation to neither the HDMI forum nor AMD could contribute the according code to the AMD driver which is part of the Linux Kernel, regarding legal implications.

Reverse engineering of binaries is pretty much a solved problem from the legal standpoint.

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fps_doug 844 days ago
It's hypothetical. There is no difference between those two scenarios, we could also just assume the hacker pulled it out of their ass...
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megous 842 days ago
Fine, but it's useless then.
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Pet_Ant 844 days ago
I mean a $1M is crowd sourceable if there was a trustworthy person to do this.
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