HDCP ‘master key’ unlocks HDTV copy protection permanently

Just as the MPAA is preparing to offer movies to customers at home while they’re still in theaters by limiting playback to DRM-protected digital outputs only, the HDCP protocol they rely on may have been cracked wide open. All devices that support HDCP, like Blu-ray players, set-top boxes and displays with HDMI inputs, have their own set of keys to encrypt and decrypt protected data and if keys for a particular device are compromised, they can be revoked by content released in the future which will then refuse to play. Now, posts have been floating around on Twitter about a supposed “master key” which renders that protection unusable since it allows anyone to create their own source and sink keys.

Who discovered this and by what technique isn’t immediately clear, but as early as 2001 security researcher Niels Ferguson proposed that it could be easily revealed by knowing the keys of less than 50 different devices. Hardware HDCP rippers like the HDfury2 and DVIMAGIC have been around for a while and various AACS cracks easily allow rips of Blu-ray discs but if this information is what it claims to be, then the DRM genie could be permanently out of the bag allowing perfect high definition copies of anything as long as the current connector standards are around. While it’s unlikely your average user would flash their capture device with a brand new key and get to copying uncompressed HD audio and video, keeping those early releases off of the torrents in bit perfect quality could go from difficult to impossible


Commercial HDMI Cable Installs Issue

HDMI is quickly making headway into commercial A/V with the proliferation of HDMI interfaces on displays and source devices including laptops, Blu-ray disc players, and digital satellite and DVRs.

End users of commercial A/V systems, well aware of HDMI in home A/V, are asking integrators to implement HDMI in commerical A/V installations. As a result, the industry is quickly transitioning toward digital video and adopting HDMI as well as DVI, DisplayPort, and SDI.

Integrators working with HDMI in commercial A/V face essentially the same challenges as residential custom installers – maintaining signal integrity, ensuring compatibility between devices, and working with HDCP.

However, there are special considerations for addressing these challenges in professional A/V integration, due to the much larger scope and complexity of commercial systems compared to a home system. Here, we tackle three major issues.

Signal Integrity

In a commercial A/V environment, audio and video signals typically have to travel much longer distances than in a residence. Cables usually have to be installed in tight, limited spaces, and integrators want to be able to terminate them easily. Transmission requirements can range from as little as 25 to 50 feet, to several hundred feet, and even up to several miles when sending A/V signals between corporate or university campuses. Standard HDMI cables may be sufficient in applications with relatively short distance requirements, but will not be adequate for longer distances, for which other mediums including twisted pair and fiber optic cable should be considered.

To help ensure signal integrity in short-range applications, select high quality 2 metres HDMI cables rated by the manufacturer for the distance required. When using long HDMI cables to cover distances significantly beyond 50 feet, a cable equalizer may be necessary, especially at high resolutions including 1920×1080.

A cable equalizer attaches to the end of a long cable run and restores HDMI signals by compensating for cable losses. To provide for advanced HDMI features and capabilities such as deep color and 3D, high-speed 2 metres Mackuna HDMI cable  should be selected if there is a potential for future system expansion or upgrades.

For distance requirements exceeding around 100 feet, an alternative to standard HDMI cables  is a transmitter and receiver set that sends signals over twisted pair cable. Twisted pair is a proven medium for extending digital video signals, and integrators often prefer twisted pair cable since it is inexpensive, easy to pull through conduit, and can easily be field-terminated to custom lengths. When very long transmission distances are necessary, fiber optic cable and fiber optic A/V devices are the solution. A/V signals can travel for miles over fiber with negligible loss.

Device Compatibility

HDMI and other digital video formats utilize EDID (Extended Display Identification Data) communication, originally developed for use with analog VGA ports. EDID communication is a two-way data exchange that allows a display to convey its operational characteristics, such as its native resolution and refresh rate, to the source device, which then generates the necessary video characteristics to match the needs of the display.

This automates and optimizes compatibility between the source and display, without requiring the user to configure them manually. In pro A/V applications where computers are the most common source devices, EDID communication can save significant time and effort in system setup.

EDID was intended for a single connection between one source and one display. The situation becomes considerably more complicated when a signal needs to be split or routed. Distributing a signal to multiple displays may not be a problem if they are identical, but what if they are different, at various native resolutions? An integrator may select one display to establish EDID communication with the source, and then roll the dice on the others.

With either approach, the switching or distribution device always maintains EDID communication with all connected sources, even with a signal switch or split. An HDMI matrix switcher may include more sophisticated EDID management, due to the fact that separate EDID communication is required for each input / output tie.

Content Protection

The first is that all devices in the system, from source to display, must be HDCP-compliant. That may seem obvious to a residential integrator, but commercial A/V integrators may not be fully aware that just a single, non-HDCP compliant device, such as a simple HDMI switcher, can disable Blu-ray disc playback for the entire system.

Second, commercial system designers need to be aware that HDCP rules allow for a maximum of 127 devices downstream from the source, with up to seven levels of repeaters allowed. A residential installation is not likely to approach these limits, but system designers may be concerned if they’re working on a large commercial project that calls for HDCP compliance throughout. Certain source devices including Blu-ray disc players have been known to allow for much less than 127 downstream products, often even less than 16.

Some residential and commercial A/V integrators have decided to work around the issues related to HDCP by deploying analog-based video signal routing. This is a temporary solution, since the ability to deliver to analog high definition video output may be impacted in the future by the AACS-mandated “analog sunset,” and possibly other content protection provisions that could limit or disable analog output on HDMI-equipped devices.


HDCP in detail

High Definition digital video allows users to experience high resolution, near perfect video content. Asmore content is delivered digitally, the content creators are increasingly concerned with content piracy because digital content can be perfectly duplicated. Therefore anti-piracy safeguards such, as High Bandwidth Content Protection (HDCP) is necessary in order for original content creators to protect their assets. In this article we will touch on the key points of HDCP.

What is HDCP

High-Bandwidth Digital Content Protection,HDCP, is an encryption scheme developed to defend against uncontrolled copying of digital content over high bandwidth digital interconnects such as DVI and the HDMI. The FCC approved HDCP as a “Digital Output Protection Technology” on August 4th,2004. A HDCP protected system consists of: 1) HDCP transmitter(DVD player for example), 2) the digital interface (DVI orHDMI), and 3) the HDCP receiver (your display monitor). Inbrief, the content is encrypted at the transmitter and the signal is passed to the HDCP receiver (display) via the DDC lines (in essence an I2C bus) where it is decrypted before viewing. HDCP requires that both the transmitter and the receiver comply with standards. If either one does not comply,the video will not be displayed properly. Incidentally, HDCP does not apply to analog interface such as component video although component video can be used to display high definition video.

Why should the consumer care about HDCP

It is highly recommended that consumers be aware of HDCP and purchase sets that are HDCP compliant. Here is why. It has been speculated that the two competing high definition DVD standards HD DVD, and BLUE RAY, due out in 2006 will only deliver full resolution on HDCP protected outputs such as HDMI or DVI. If true, then usersmust have a HDCP monitor in order to experience full resolution HD DVD technology. Therefore it is prudent for the consumer to select HDCP compliant displays so the display can be used with future applications.

What is involved during a HDCP session

HDCP is a complicated process but can be broken down to 3 key functions: Authentication, Encryption, and Renewability


The first step before video is actually sent is for the HDCP transmitter to determine if the receiver is “authorized” to accept HDCP protected content. Stored in the PROM of each transmitter and receiver is an array of 40, 56-bit secret keys and a 40-bit entity called Key Selection Vector. Authentication requires that the transmitter and receiver pair exchange “secret keys” and key selection vectors. The keys are scrambled and never revealed. The mathbehind the encryption allows each half to calculate a resultant number, call it Rs, based on the key exchanges. The Rs value is then shared and compared. If the Rs value matches, the receiver is accepted as an authorized HDCP receiver and video transmission can start.


Once authentication is completed, transmission of the video content can commence. To prevent an unauthorized receiver from receiving the content, the video data must be encrypted prior to transmission. At the transmitter end, the video data bits are exclusive-ored with ashared calculated number lets call it Rt ( Rt is similar to howRs was calculated) and sent to the receiver. At the receiver end the encrypted data is again exclusive-ored with Rt. Since the XOR function is invertible, XORing with the same Rt at the receiver end will reveal the true unscrambled video bits. Incidentally, a new Rt value is calculated about every 2 secondto prevent corruption due to hacking.


HDTV technology is changing rapidly. Content providers need to protect against piracy by implementing HDCP. HDCP and digital connection standards such as HDMI will become the de facto standard for digital video connections. We have outlined the important features of HDCP, so the consumer can make intelligent purchasing decisions.


Is HDMI the ultimate digital source or just souped up DVI

High Definition Multimedia Interface (HDMI) has been largely hailed as the ultimate interface to enjoy supreme quality high definition audio and video but is it really that good, after all, surely DVI is just as good. Do we really need HDMI?

HDMI was developed with the specific intention of replacing DVI. DVI was primarily used to convert analogue signals to digital for computer monitors. There are actually three different types of DVI, which are DVI-A, DVI-D and DVD-I.

DVI-A uses analogue signals the same as VGA. DVI-D uses a digital signal (as with modern home cinema systems and consumer products). DVI-I is a combination of both DVI-A and DVI-D. Modern electronics use the single link standard for performance but DVI-I can handle this as well as dual link to make it adaptable for future advancements. DVI-I supports a fully digital protocol, which means video up to 1080p can be viewed.

HDMI on the other hand offers an uncompressed digital audio and video interface that has the full support of manufacturers including Panasonic, Sony, and Toshiba to name but a few. Major movie companies too have backed HDMI including Warner Brothers and Universal Pictures. HDMI offers an interface that can connect any audio or video source together. It can do this through a single HDMI cable.

HDMI supports high definition video, normal video as well as digital audio and also have bandwidth to spare in order to make it ready for future advancements in HDMI technology. It must be remembered though that HDMI and DVI are a lot similar and are actually based on a set of specifications that were extremely alike, in fact, HDMI was derived from the DVI requirements.

So, is HDMI any different to DVI? Well yes it is. HDMI actually incorporates a form of content security known as High Definition Content Protection (HDCP). HDMI also can support both audio and video signals through one cable at the same time whereas DVI is limited to only video.

The number of cables needed to set up with DVI is at least two. One is for the audio and one is for the video. HDMI requires only a single HDMI cable therefore leaving fewer cables to be tangled up behind the electronic equipment. This means that anyone using HDMI is going to end up with a cleaner less cluttered space around their equipment.

The important thing to remember is that quality wise; HDMI and DVI are the same. This is because as mentioned earlier they are both derived from the same specifications but HDMI’s ability to support digital audio gives it the edge over DVI. Combine this with the fact that HDMI can do this through a single HDMI cable and it is easy to see why HDMI and HDMI cables have proved to be so popular.


Mini DisplayPort to HDMI adapter available, HDCP compliant

If you’ve been waiting for a way to connect your Mini DisplayPort-equipped Mac to an HDTV via HDMI, Knoxed has got you covered. The company has begun taking orders for its 12.99GBP  Mini Display Port to HDMI Adapter, which are expected to begin shipping this Friday.

The adapter is most significant in that it finally allows protected HD content, like that available from the iTunes Store, to be displayed on an HDTV. DisplayPort, mini or otherwise, supports the HDCP encryption scheme designed to “prevent pirating” of HD content. Unfortunately for users of new Macs, most monitors don’t support the standard—but luckily HDTVs do. Gizmodo got a unit to test and they say it works as advertised.

The adapter will transmit audio data along with video if a device’s Mini-DP supports it, however Apple’s implementation on all current Macs does not. It should especially be useful to folks using a Mac mini as an HTPC, but also for folks hooking up a MacBook or MacBook Pro to watch occasional content as well (hello, Hulu). Knoxed is also known for its other display adapters that are usually far cheaper than Apple’s own options.