High-bandwidth Digital Content Protection (HDCP) safeguards the transmission of copyrighted AV content. HDCP 2.x is in many ways different from HDCP 1.x, and likely to cause as many interoperability issues as its older brother did – unless system designers understand a few key points. The formats are not compatible, but awareness of the differences and similarities, along with the relationship to HDMI 2 and 4K, will help you ensure seamless end-to-end support for old and new HDCP material in all your installations.
1 THE SOURCE MAKES ALL DECISIONS
It is important to understand this first, and it makes good sense when you think about it. The source is the gatekeeper of the content, whether that content is delivered via the internet or a spinning plastic disc. The source knows the demands of the content itself, and implements those demands by enabling HDCP protection or not.
2 HDCP 1.X AND HDCP 2.X ARE NOT COMPATIBLE
Not compatible? It’s okay. There’s no real problem with that. A year ago, the source’s decision was simple: to enable HDCP or not. But in the past year or so, a new version of HDCP has entered the world. (Note: the latest versions of the two major HDCP revisions are HDCP 1.4 and HDCP 2.2. The minor differences in the sub-version number – e.g. HDCP 1.2 vs 1.4, or HDCP 2.0 vs 2.2 – are not critical to understand. Therefore, I use the shorthand “HDCP 1.x” and “HDCP 2.x” to refer to the two major versions that now coexist in the market. In fact, practically all real products use versions 1.4 and 2.2 exclusively.) HDCP 2.x is a complete re-write of the HDCP specification, with no backward compatibility. That sounds terrible, but in fact it’s not a big problem. There are no HDMI transceiver chips that provide HDCP 2.x without support also for HDCP 1.x. Both systems are included on the same chip. This means the products you encounter that support HDCP 2.x will also support HDCP 1.x.
3 HDCP 2.X OFFERS MUCH STRONGER ENCRYPTION
A major component of any content protection scheme is its encryption. HDCP 1.x used a custom-built scheme designed to be simple and cheap to implement. This may be why HDCP 1.x was “cracked” in 2010. In September of that year, Intel (the creator of HDCP) confirmed that a master key had been made public. This key makes it possible to generate valid decryption keys and totally defeat HDCP 1.x protection. A key upgrade to HDCP 2.x is the use of AES-128 encryption. This is the same encryption used for secure government and business communication all over the world. If AES- 128 is broken, we’ll have bigger problems than a few pirated movies!
4 THERE ARE NO TECHNICAL LINKS WITH HDMI 2.0 OR 4K
This one is simple. There is nothing in the HDMI specification that says you have to use HDCP 2.x (or, for that matter, that you must use HDCP at all). And by extension, there is no technical rule or standard that says 4K content must be protected by HDCP 2.x.
5 THERE ARE DE FACTO LINKS
Practically speaking, we will see all Hollywood 4K content demanding HDCP 2.x protection. HDCP 2.x was really invented by and for Hollywood, who felt that the protection offered by HDCP 1.x is not sufficient for their valuable 4K intellectual property. This is probably a reasonable position, considering the broken cryptography of HDCP 1.x.
6 EVERY SINGLE DEVICE IN THE CHAIN MUST COOPERATE
Once a source has decided on the content protection required, the content goes out with the protection applied. Of course this means that the display device must support the same level of protection in order to decrypt the signal. But it also means that every piece of electronics in the chain – transmitters, receivers and switches – must support the content protection. If you have a source insisting on HDCP 2.x and a three year old HDMI switch that can only support HDCP 1.x, you get a dead end and a black screen.
7 SOME HDCP 2.X CONTENT CAN BE DOWNGRADED TO HDCP 1.X
This again comes down to decision making by the source, driven by the content. The first 4K Blu-ray player to hit the market (by Samsung) will allow an image out with only HDCP 1.x protection. However, when it allows this, it forces the image to the scaled down to 1080p. Again, this is a demand of Hollywood – that their 4K content must be protected by HDCP 2.x. There is no guarantee that a source will behave this way, so it is certainly best to assume you will need HDCP 2.x gear everywhere.
8 HDCP 2.X IS ETHERNETFRIENDLY
HDCP 2.x finally means that protected content (even HDCP 1.x) may be moved across an Ethernet network. Despite claims (and products!) from various manufacturers of video-over- IP gear, the HDCP 1.x specification is very clear about what can (and what cannot) be done with HDCP 1.x protected content. It cannot be transmitted across an Ethernet network without violating that specification. HDCP 2.x has introduced a new set of rules and techniques which finally do allow this. In fact, even HDCP 1.x content may be upgraded to HDCP 2.x, transmitted across the network according to HDCP 2.x rules, and then downgraded to HDCP 1.x content for output to a display at the far end. HDCP 2.x content may also be transmitted across Ethernet, but of course must still be protected by HDCP 2.x at the end.
Justin Kennington is director of strategic and technical marketing at AptoVision, a developer of advanced chipsets for AV signal distribution.