High-Bandwidth Digital Content Protection
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HDCP (High-bandwidth Digital Content Protection) is a specification (http://www.digital-cp.com/data/HDCPSpecificationRev1_1.pdf) developed by Intel Corporation to "protect" digital audio and video content as it travels across Digital Visual Interface (DVI) or High Definition Multimedia Interface (HDMI) connections. The HDCP specification is proprietary and implementation of HDCP requires a license. It is a form of Digital rights management.
HDCP is licensed by Digital Content Protection, LLC (http://www.digital-cp.com/). In addition to paying fees, licensees must also agree to limit the usefulness and interoperability of their products by restricting outputs and lowering the quality of reproduction on some interfaces such as speaker cables. Licensees cannot allow their devices to make copies of content, and must design their products to "effectively frustrate attempts to defeat the content protection requirements."
Researchers demonstrated fatal flaws in HDCP for the first time in 2001, prior to its adoption in any commercial product. Scott Crosby of CMU authored a paper with Ian Goldberg, Robert Johnson, Dawn Song, and David Wagner called A Cryptanalysis of the High-bandwidth Digital Content Protection System (http://apache.dataloss.nl/~fred/www.nunce.org/hdcp/hdcp111901.htm). This paper was presented at ACM-CCS8 DRM Workshop on November 5th, 2001.
The authors conclude, "HDCP's linear key exchange is a fundamental weaknesses. We can:
- Eavesdrop on any data
- Clone any device with only their public key
- Avoid any blacklist on devices
- Create new device keyvectors.
- In aggregate, we can usurp the authority completely."
Around the same time that Scott Crosby and co-authors were writing this paper, noted cryptographer Niels Ferguson independently claimed to have broken the HDCP scheme, but he was unable to publish his research due to legal concerns arising from the Digital Millennium Copyright Act.
The Federal Communications Commission approved (http://hraunfoss.fcc.gov/edocs_public/attachmatch/DOC-250532A1.pdf) HDCP as a "Digital Output Protection Technology" on August 4th, 2004 despite its known flaws. FCC regulations will require digital output protection technologies on all digital outputs from HDTV signal demodulators as of July 1st, 2005 (http://www.eff.org/broadcastflag/). Analog outputs from digital receivers do not require output protections, despite the fact that converting signals between analog and digital is trivial and can result in imperceptibly degraded signals when using an analog-to-digital converter. The HDCP standard is more restrictive than the FCC's Digital Output Protection Technology requirement. HDCP bans analog outputs from compliant products, presumably in an attempt to reduce the size of the analog hole in HDCP devices.
On the 19th of January, 2005 the European Industry Association for Information Systems (EICTA) announced (http://www.eicta.org/dls/Common/GetFile.asp?&logonname=guest&ID=9719&mfd=off) that HDCP is a required component of the European "HD Ready" Label.
External links
HDCP (http://www.theprojectorpros.com/learn.php?p=theater_hdcp) HDCP Encoding and Decoding - What Does This Mean to You? (theprojectorpros.com)de:High-bandwidth Digital Content Protection