HDMI HDCP handshake - Can I disable this?

alexis

New Member
I would like to know if I can use a custom firmware to disable HDCP on the HDMI output, I know you can disable it for SD content even on stock firmware but I would really like to disable it altogether. There is a story behind this.

The story, ill try and keep it concise:

FOXSAT HDR 500GB - > HDMI - > Sony STR-DH520 - > HDMI - > Philips BDL5531EL
XBOX One - > HDMI - > Sony STR-DH520 - > HDMI - > Philips BDL5531EL
Been working fine for years but last week when watching Freesat the display would freeze on the current frame and the audio would carry on fine from the AMP. When watching plex via the xbox it would work fine for a while but then it would part freeze.

FOXSAT HDR 500GB - > HDMI - > Sony STR-DH520 - > HDMItoDVICable - > Philips BDL5531EL
XBOX One - > HDMI - > Sony STR-DH520 - > HDMItoDVICable - > Philips BDL5531EL
The xbox will work fine all day long no issues at all but the Freesat box is not working via DVI, I get a message generated from the TV along the lines of incorrect setting or format or something like that.

FOXSAT HDR 500GB - > HDMItoDVICable - > Philips BDL5531EL
Freesat box is not working via DVI, I get a message generated from the TV along the lines of incorrect setting or format or something like that.

FOXSAT HDR 500GB - > HDMItoDVICable - > Some other PC monitor
Wasent able to connect to sat cables where is was buy played recordings back for hours on end without issue.

XBOX One - > HDMItoDVICable - > Philips BDL5531EL
The xbox will work fine all day long no issues at all.

XBOX One - > HDMI - > Philips BDL5531EL
Freezing issues.

As you can see the combinations I have tried suggest I have more than one problem and its a nightmare to diagnose as the problem only seems to present itsself after a number of hours suggesting heat buildup.

Because the xbox one will work fine through the Sony AMP using the TVs DVI port I have ruled out a problem with the AMP.

When I do involve the AMP in one of the problematic setups the problem is exaggerated. For example I get a no signal error from the TV intermittently before any eventual freezing. This has caused me to suspect the chain of HDCP handshakes falling over.

I have tried a few HDMI cables

I have reset all configuration on the TV.

I have reset, formatted and also tried Raydon's firmware on the Foxsat.

I considered getting a HDCP stripping HDMI splitter but I suspect the device would still need to handshake with the FOXSAT before stripping it.

I'm really stuck for cash right now otherwise I would invest in a new TV but even then I don't know know if that is gonna fix the problem. I would like to hope the silly handshake problem I have seen described online has cooked the chip inside the TV responsible for handshaking on the HDMI port specifically and that disabling HDCP will somehow get the Foxsat box working on the TVs DVI port.

Sorry its so long...
 

Black Hole

May contain traces of nut
Methinks you don't understand the purpose of HDCP. It stands for High-bandwidth Digital Content Protection, and is a licence requirement for the delivery of HiDef content over HDMI (for more info see Glossary - click), and as such Humax must enforce its use in order to comply with their licence to use proprietary hardware/software.

The custom firmware only adds the ability to run additional code alongside the Humax code, the very few exceptions being where it has been possible to analyse the Humax code (which is not documented and only readable as machine code binaries) sufficiently to make very slight tweaks such as Nowster's patch.

You're lucky HDCP can be disabled for StDef - the Freeview equivalent (HDR-FOX and HD-FOX) have it running all the time.
 
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OP
A

alexis

New Member
Methinks you don't understand the purpose of HDCP. It stands for High-bandwidth Digital Content Protection, and is a licence requirement for the delivery of HiDef content over HDMI (for more info see ), and as such Humax must enforce its use in order to comply with their licence.

You're lucky it can be disabled for StDef - the Freeview equivalent (HDR-FOX and HD-FOX) have it running all the time.

Nope, I understand 100%, I tried to make my question obvious by stating it in the first line:

I would like to know if I can use a custom firmware to disable HDCP on the HDMI output.

The rest of my post was an attempt to explain why I would like to do that, but thanks anyway.
 

Black Hole

May contain traces of nut
I think you read my post before I finished composing it:
The custom firmware only adds the ability to run additional code alongside the Humax code, the very few exceptions being where it has been possible to analyse the Humax code (which is not documented and only readable as machine code binaries) sufficiently to make very slight tweaks such as Nowster's patch.

Nope, I understand 100%, I tried to make my question obvious by stating it in the first line
That's as may be, but if you understand the purpose of HDCP you will realise it isn't going to be made easy to overcome, and may even be implemented in hardware (or at least at a very low level of firmware).
 
OP
A

alexis

New Member
I think you read my post before I finished composing it:
That's as may be, but if you understand the purpose of HDCP you will realise it isn't going to be made easy to overcome, and may even be implemented in hardware (or at least at a very low level of firmware).

Correct, I responded before you edited it.

I understand the purpose and never suggested it would be easy, I just didn't see an option and wondered if it had been done as simple as that. A "no im afraid not" would have been fine.

Thank you for confirming.
 

MofTot

Member
You can purchase a naughty HDMI splitter that strips away HDCP.

The non-conforming (because they remove HDCP) splitter boxes can be difficult to get hold of, the one I purchased on Amazon UK is no longer available.

You should be able to find one on Amazon UK/eBay UK, check the descriptions or with the seller that they actually remove HDCP.
 

Black Hole

May contain traces of nut
It can't remove HDCP entirely - it must be able to complete the cryptographic handshake locally and then pass on the subsequent HDMI stream. Consequently there may be the same difficulties (or worse) getting a source to play ball (unless it is somehow better at doing it than a legitimate TV).

It seems to me there are three ways to do this: crack the code securing the handshake; steal the code from a licenced user; obtain a chip with the code already enbedded in it. In either of the first two cases, once available there would be no restriction of supply, so my guess is that somebody acquired a batch of chips which are limited in number and therefore restrict availability.
 

MofTot

Member
Not sure precisely how it does it but it handles HDCP in a way that enables you to record the HDMI stream unencrypted.
 

Black Hole

May contain traces of nut
Indeed, but the HDCP is still used to control whether the source outputs data at all. The "magic box" completes the handshake on behalf of the destination (devices capable of recording an HDMI stream are not supposed to be capable of completing the handshake).

What I am saying is that a source unit with a flakey HDCP will still have a flakey HDCP, whatever means is being used to negotiate with it.
 

Black Hole

May contain traces of nut
This is an interesting summary (it's like a blog so the individual articles are in reverse order of time, to follow chronologically read from the bottom): https://hackaday.com/tag/hdcp/

I'm a little confused, the remarks seem to indicate that the HDMI link itself is encrypted and I had been under the impression that only the negotiation was encrypted. If that's the case, it makes more sense that a stripper could help (providing the stripper performs more reliably than the original equipment).

I also found this (no idea how trustworthy the information is, but it seems to support my original interpretation): https://security.stackexchange.com/questions/124762/how-does-hdmi-splitter-bypass-hdcp
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).

I've also read that keys can be revoked to "blacklist" units which are known to be compromised - the question is how is this blacklist distributed? Are all our HiDef HDMI sources "phoning home" to pick up blacklist updates?
 
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grahamlthompson

Well-Known Member
Not sure if this is relevant but may cast some light. I use an HDMI output from my AV amp to feed a local TV and a cat6 single cable pair of baluns to feed a kitchen TV. Input to amp includes two HRD-Fox-T2's and a HDR-1000S. Both destination devices are Full-HD 108050/60 capable. Picture was great on both but turning off the kitchen TV blanked the main TV output. A cheap HDCP stripping splitter from e-bay in the feed to the kitchen TV sorted out the issue.
 
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Mike0001

Well-Known Member
The blacklist is on any new media, but defeat devices can randomly generate a valid key, so that makes that useless.$
 
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