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Comment by __s | Hacker News Reader

Concrete solution is an HDMI adapter splice that can record to a USB drive whatever passes through it

This may not always work, data going through HDMI is frequently encrypted. If you try to capture the data between a Blu-ray drive and a TV (for example), it will be encrypted.

But there must be a point, where you still have full digital original signal, but decoded. It has to be possible.

I believe the private keys are in the TVs themselves. Not sure how accessible the keys are.

I could be wrong, but I was under the impression that you can get cheap Chinese HDMI splitters that strip the encryption.

I would think it has to be relatively easy to decrypt given that the Blu-Ray player has to either send a decryption key to the TV via the HDMI cable, or the TV has to already have a decryption key that could presumably be skimmed.

From what I can tell the splitters essentially convince the playback device to play by relaying whatever HDCP messages the TV sends:

    Playback Device (Roku etc)
               |
               |
           Splitter ------ Unauthorized Player (Recorder)
               |
               |
    Authorized Player (TV)

Without this the Playback Device will show a black screen, an HDCP error message or something similar, but even with the splitter & an authorized player it seems the content can be encrypted.

Since the TV obviously has the capability of decrypting the content it seems like there should be a way to split the signal somewhere between the main TV board and the display panel(s), which sounds like a big deal. Or maybe someone could make an incomplete splitter / recorder that just needs a legit Samsung board attached to it?

I did a Google because I was curious, and some of them do indeed strip the HDCP.

I think what you're saying is basically what's happening. The HDMI splitter pretends to be a display/TV, so the playback device sends encrypted data to the splitter, which decrypts it and forwards the decrypted part over the HDMI connections.

From what I could find, it's usually the cheap HDMI splitters that emit unencrypted data over the HDMI ports. That kind of makes sense; they implement HDCP inbound because they have to, but they leave HDCP off the output ports because it reduces their manufacturing cost.

I think you can't just "forward" the encrypted packets, because then both outputs on the splitter would try to communicate back to the player, causing issues. The splitter has to MITM the connection.

https://www.tweaking4all.com/home-theatre/remove-hdcp-hdmi-s... has some cursory info, and links to HDMI splitters that strip HDCP (not an endorsement of whatever you do with them, just an interesting device).

They exist. My cheapo $20 USB HDMI capture card does it too and I can use OBS to record Blu-rays off my PS3 for example.

Is that what they used to "record" amazon, disney, etc. movies and tv shows ? I was still picturing social/computer hacking.

Although Blu-ray encryption was cracked back in 2007.

https://knowyourmeme.com/memes/09-f9-11-02-9d-74-e3-5b-d8-41...

But backdoor keys for authorities will not suffer this problem. Trust me. /s

That's not correct. Version 1 of their system was, they quickly fixed it to the chagrin of many Linux desktop users (who just want to play and watch the movies they paid for on the hardware they own).

So we're back to the state of you don't actually have property rights in any of the things you own or paid for.

bluray encryption was never "cracked". even the above link is clear that it wasn't a crack. just that the encryption mechanism was well understood, but it requires a device key to generate the volume unique key (VUK) that is necessary to decode each individual disc. VUKs can't be revoked, but they are unique to each disc (pressing). device keys can, and when they are, they can't be used to generate a VUK any longer.

so one has 2 options, a database of VUKs that others generate (don't need a device key then) or getting a device to give up its key so that one can generate VUKs onesself. The problem with this is, that that key (if made public) will then be revoked itself.

i.e. I don't consider this being cracked, this is the encryption working exactly as designed.

Look at the FeinTech splitters for example. I’ve thrown everything from BRs to streaming at them and they can handle it all.

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