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I just read this article. It's about HDCP and how some old HDMI monitors would not work with your newer devices (such as game consoles, etc) because newer devices protect video stream content in a way that blocks old monitors from displaying it.

I'm perplexed at this excerpt:

Short of buying a new television or giving up on your video game project the only way to deal with your HDCP compliance problem is to buy a cheap HDMI splitter that ignores HDCP requests.

This does not sound right. Surely an old TV that is mentioned in the same article earlier that has no slightest idea about HDCP would also ignore HDCP requests simply by merit of not being aware of them?

Still the old TV won't work, and the splitter will. I think this article oversimplifies things to make them more accessible.

Can we dig a little bit deeper and explore, what exactly the splitter does to circumvent HDCP? The article says:

The outputting device says “Hey display! Are you HDCP compliant? Here is my license, show me your license!” and in turn the display (or other HDCP compliant device) returns with “I am! Here is my license!”

Does this mean that the splitter itself has the license in order to make the video exchange work? If not, why the outputting device does not refuse to proceed when no license is found on the splitter?

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HDCP has a built-in failure mode when it communicates with a device which doesn't support it: it downgrades the video content to standard definition (or sometimes 720p). The video splitter "trick" allows you to strip HDCP simply by the fact that it is a device which doesn't understand HDCP, and therefore never replies to the packets. The downside is that you can't watch the content in high definition, which is exactly what HDCP's threat model is built around.

You can get HDCP strippers which do contain the HDCP master key, but they're usually found in the shady corners of Chinese marketplaces like alibaba, rather than mainstream western sales channels. These are HDCP-enabled devices which contain the necessary keys, either compromised or as part of an IC taken out of a legitimate device (e.g. a TV).

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    But surely an old HDMI TV would not reply to the packets either?
    – Andrew Savinykh
    Jun 1, 2016 at 8:47
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    @zespri Some support HDCP but only a really old version, so it may send back enough that the device thinks the TV supports HDCP, but then fail. It could also be a TV which uses a compromised and revoked HDCP key, which (in my opinion) is the most horrific part of HDCP key management policy.
    – Polynomial
    Jun 1, 2016 at 9:06
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    My favourite one is 144Hz refresh rates on gaming monitors.... apparently HDCP can not run at 144Hz so one just gets to see the scrambled fuzz... It's quite "fun" to recover from too... HDCP is a mess to start with, like all DRM.
    – ewanm89
    Jun 1, 2016 at 9:18
  • @ewanm89: This is a mildly old question, but I'm bumping this out of curiosity because no search engine is going to trivially show me what HDCP "scrambled fuzz" looks like, and I'd like to find out. I'm also interested to find out what you mean by "It's quite "fun" to recover from too...". These are just idle curious questions that don't need an immediate answer, so I'm just asking this as a comment for whenever you see it. TIA! :)
    – i336_
    Nov 28, 2017 at 13:41
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    @i336_ well, here is a link to photo of the fuzz, the HDCP content is in windowed mode: ewanm89.co.uk//personal/fuzz.jpg As for recovery options, one has to stop the playback somehow and direct input seems to not work fully in this state: 1) No alt+f4 2) Just pausing it won't turn the HDCP off, so media play/pause key is out 3) Ctrl+Alt+Delete does lock windows, fuzz is still there, so one is locked blind. Remote interface works, so remote kill the process or low latency stream works (steam link), RDP laggy with video. Power interruption, could cause data loss?
    – ewanm89
    Nov 28, 2017 at 15:19

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