Here is the problem with content. Content developers want the content to not be stolen. What’s the best way to steal the content in best quality – when content is streamed by a user, insert a recording device in between that relays the content but stores a copy and thereby faithfully reproducing the content (example here). Now imagine game of thrones is being streamed from HBO’s secret data center to your smart tv but before sending the games of thrones stream to your tv, a secure connection is established between the TV and the HBO’s data center. This will ensure that the TV will be able to show the stream to you but no-body in between can copy the stream. Hence, HBO will be able to protect it’s content from getting stolen.
There are many standards for content protection and there is a new-standard for 4K. It is called HDCP 2.2 and a primer on it can be read on crutchfield. I ran into this while researching about 4K UST (ultra short throw) projectors. Sadly, not all projectors clearly list that they support HDCP 2.2 or not. I found it hard to determine the adoption of HDCP 2.2 by searching online and the projector I liked did not mention clearly if HDCP 2.2 is supported or not and I had to let of the projector.
Apparently all HDMI 2.2 cables support HDCP 2.2. This may be useful information if you find that the specs say that HDMI 2.2 is supported but HDCP is not explicitly mentioned.