Josh the Aspie’s Blog

Last time, I explained what HDCP is, and how it works.

This time I’ll be writing about problems with HDCP, and why they haven’t caused HDCP to be scrubbed.

Problems With How HDCP Works

For any discussion of why or why not one should purchase a device with HDCP installed in it, it is very important to understand problems with the way HDCP works.

According to “A Cryptanalysis of the High-bandwidth Digital Content Protection System” which is a research paper by Crosby, Goldberg, Johnson, Song, and Wagner, HDCP:

If an attacker can recover 40 public/private key pairs that span the module of public keys, then the authority’s master secret can be recovered in a few seconds. With the master secret, an attacker can eavesdrop on communications between any two devices and can spoof any device, both in real time. Additionally, the attacker can produce new key pairs not on any key revocation list. Thus the attacker can completely usurp the trusted authority’s power. Furthermore, the protocol is still insecure even if all devices’ keys are signed by the central authority.

But even if you do not have that many keys, if you have even one working ‘processing’ key, if you have even one working key, you can spoof (masquerade) as that device.

If the device key is revoked to prevent said access, thousands of people who legitimately bought the device have just been robbed of the use of this device, and the one depriving them of this use is the DCP-LLC. These people are then forced to purchase new equipment.

So as you can see, HDCP is hardly secure at all, and any attempt to enforce it’s security measures against compromised keys will cause the public to use millions of dollars in devices that are no longer usable.

So why HDCP?

With all of the problems presented, why would big media even consider using this particular scheme?

The answer to this question will come in three sections.

1. Why Big Media Wants DRM in General
2. Why Big Media Wanted HDCP in particular
3. Why Big Media Decided to Keep HDCP

Why Big Media Wanted HDCP in particular

HDCP is actually designed to work in a specific segment of the digital world. Other protections prevent HD-DVDs and BlueRay disks from being played in devices that aren’t secure. But if those devices then output to an unsecured transmission media, they can be copied. HDCP was designed to fill that goal.

In order to minimize the ability to hack into HDCP, HDCP was designed to be hardwired into the silicon of various devices. However, any chip that you put into an electronic device carries a cost with it. In an effort to minimize the cost, certain limitations were placed on how complex the circuitry could be. According to the scholarly paper I referenced above by Crosby et all, the designers of the circuitry decided to limit themselves to be able to implement the logic in under 100,000 gates. This, combined with the desire to allow hookups to work without any user intervention, immediately disqualified the use of any more secure algorithms.

According to behardware.com, Intel developed this technology at the behest of the movie industry. Combined with the access and copy protections placed on their HD-DVDs and BlueRay disks, they are forcing most electronic companies to play ball. With the current state of things I have probably spent about 20 hours total shopping, and still have not been able to come up with an HDTV without HDCP.

Why Big Media Decided to Keep HDCP.

Keep in mind, some of these are only reasons why I think Big Media decided to keep HDCP, not hard facts.

Opinions are given in order of increasing insidiousness.

1. It takes time to develop any kind of cryptosystem. They already spent time and money developing HDCP. They would have to start mostly from scratch in order to use another system.
2. Microsoft adopted HDCP, and has whole heartedly embraced DRM as a whole. In fact, the operating system treats it’s self as being a HDCP compliant device, and plans to require any device plugged into it to be HDCP compliant, or the content outputted will be taken down to non-HD levels.

   You might not even get that option, your monitor or sound card might not even be able to send video or sound at all. If people stoped making HDCP compliant devices, they wouldn’t be able to interface with Vista. In my opinion that isn’t to bad of a thing, but many consumers and other companies disagree.

3. Since HDCP definitely doesn’t work, and according to an analysis on “Freedom to Tinker” it could be fixed with a bit more resources, one has to wonder why they didn’t choose to fix it before it became wide spread. Well, the explanation is relatively simple, and the author of “Freedom to Tinker” seems to agree.

   Due to the DMCA it is illegal to bypass or post systems to bypass DRM measures. They also have recourse for huge numbers of lawsuits. In fact, if damages exceed a certain amount, you can be sent to jail for up to 10 years for doing so.

   So it seems that the main reason to keep DRM around is to allow for lawsuits and criminal actions against ‘pirates’ who just want to help other people use the technology they bought.

4. Since any compromised keys will be revoked, and since devices with revoked keys will become little more than useless, it seems like it is actually in the best interests of the electronic manufactures to cooperate.

   After all, that means consumers will have to wind up buying more electronic equipment, and will get used to buying and throwing out electronics more often.

This entry was posted on Thursday, August 2nd, 2007 at 12:14 am and is filed under Technology, Entertainment, Political, Current Events. You can follow any responses to this entry through the RSS 2.0 feed. You can leave a response, or trackback from your own site.