No, H.D.C.P. is not short for HANDICAP... it is an acronym for "High-Bandwidth Digital Content Protection". Think of it as a modern digital version of Macrovision™ (most prevalent for many years on pre-recorded VHS tapes). It's included in the HDMI bitstream to stop the pirating of master quality digital sources, namely movies and the like.

The truth is that without HDCP the owners of the intellectual property that is supplied on DVDs etc (eg movie studios and production companies) would not allow us all access to such high quality video and audio in the first place. If HDCP was not present in the DVI or HDMI bitstream, it would be made possible for pirates to make high definition copies of movies that are indistinguishable from the originals, which of course is highly illegal and would do irrepairable damage to the industry. For this simple reason, HDMI would not have been allowed to introduced without some form of protection.

HDCP was developed by Intel Corporation as a "Digital Rights Management" (DRM) solution, and introduced exclusively on DVI during its midlife. HDCP went on to become a standard component of the original specification for HDMI, and remains so to this day. Once you begin to understand how HDCP works, and why, you'll see that it not a 'handicap' at all... So how does it work?

HDCP - the keys to High Definition

HDCP is a licensing system, much like HDMI, managed by Digital Content Protection, LLC, a subsidiary of Intel Corporation. All licensees must pay membership fees and sign an agreement to abide by the stipulated regulations as to the application of HDCP.
HDCP is a far more clever system than the old analogue Macrovision in that it can still allow the passing of content, but in a restricted capacity. For example, a standard resolution DVD with analogue audio may not be restricted by HDCP at all, depending on the owners' requirements, but any high definition video and digital audio content may be restricted. The restriction may be that it can only be viewed on a HDCP compliant display (plasma, LCD, projector etc), but cannot be successfully connected to the input of a digital recording device such as DVD-R, at least not via DVI or HDMI.
A licensee of HDCP is issued with a unique set of digital 'keys', which is a string of binary code - digital "I"s and "0"s, supplemented by a "Key Selection Vector" (KSV) code. A licensee agrees to keep the details of their unique 'keys' secret, otherwise they will be in breach of their licensing agreement. When two HDCP compliant devices are connected together, they exchange KSVs. Without getting into any further technical detail, the firmware in each device will determine whether the two components are authorized to 'talk' to each other fully before encrypting and passing the content from source (transmitter) to sink (receiver).

If a set of HDCP keys are not present or are unauthorized to pass the content, then either a restricted quality output, or no output at all will result.

Restrictions

The main restriction in the application of HDMI enabled devices is the under development of HDCP in DVI supporting devices (ie pre-HDMI), especially in the I.T. field. DVI is forward compatible to HDMI, but only where HDCP is present. Not all DVI supporting devices will be HDCP compliant, and connection of such devices to a HDMI/HDCP display may result in no picture or sound.
A good example of this is the video card on a PC. Many are equipped with a DVI ouput, but many will not support HDCP. This is due to the fact that computer monitors will generally not require HDCP authentication as they are made for computer graphics, not IP sensitive content like movies. This hasn't really been an issue in the IT world, but may cause problems if you want to use your PC as a home theatre component to a HDCP display. In this case the display will be looking for a HDCP authentication key from the source and will not find one, and a blank screen may result.

The solution? Use only HDCP compliant sources and accessories (switchers etc) for reliable results. Just using a DVI-HDMI adapter does not ensure a complete HDMI bitstream.

Specifications and operation

There are two HDCP versions - 1.0 and 1.1. For the sake of simplicity, it can be said that 1.0 was the original spec for DVI, and 1.1 is the current spec for HDMI. Only 1.1 is currently being licensed.
HDCP follows the following process for operation. Each entire process is repeated for each and every frame of video being transmitted;
  1. KSV (Key Selection Vector, comprising 40 bits with exactly 20 bits set to "1" and 20 set to "0") are exchanged between transmitter (source) and receiver (sink/display) devices
  2. Each device adds its own secret "Key" contents - 40 keys, each 56 bits long
  3. If a particular KSV is set to 1, then the corresponding key is used (40 bits of KSV linked with 40 secret keys). KSV bit set to 0 results in the corresponding key being ignored in the addition
  4. The algorithm process ensures that both KSVs and keys get the same resultant 56 bit number, of which is later used in the encryption process.
  5. Each decoded pixel is encrypted by an included generator and packaged in the HDMI TMDS bitstream.
  6. Once the frame is complete (ie all pixels encoded and transmitted), the process of key exchange etc begins again
When I first heard about HDCP encoding and the use of these digital "keys", I must admit that I wondered how a new device on the market could be recognized by an older device with HDCP. I thought it would be a bit like Microsoft® Windows™ not having the drivers to run some new hardware - an Windows update would be required to include the new hardware automatically, or alternatively it would require the installation of drivers from the hardware manufacturer.

With HDCP it is not like this. It does not require the use of an established database with updates. The method used ensures reliable results from literally millions of KSV/key combinations - one that is always current. It does this with a complex (for most of us, anyway!) algorithm which effectively combines keys to result in a consistent 56 bit number, and hence no incompatibilites between different generation of HDCP compliant hardware. That is, it verfies the devices with a method of calculation rather than reference.

To view the full HDCP v1.1 specification, please click here (465k - file size; download recommended)

 

 

            

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