German boffins have pulled off a successful attack on HDCP copy protection – using cheap hardware and a lot of clever coding.
Intel's HDCP (high-bandwidth digital content protection) allows the encrypted transfer of high definition video signals via DVI, HDMI, DisplayPort and other connectors and between TVs and Blue-ray discs or set-top boxes. The HDCP master key was leaked last year but there was no easy way to exploit this.
Rather than trying to design a customised chip (both expensive and complicated), computer scientists in the Secure Hardware Group at Germany's Ruhr University built a custom board using relatively inexpensive FPGA chips. A Xilinx Spartan-6 FPGA featuring an HDMI port and a serial RS232 communication port was created and sat between a Blu-ray player and a flat screen TV, intercepting and decrypting traffic, without being detected. The rig, which cost little over $200, was built by professor Tim Güneysu and PhD student Benno Lomb, as part of a research project in copy protection.
Although the exercise shows that HDCP is vulnerable to practical attacks the whole exercise is of little interest to pirates, who can more easily tap compressed high-definition content from receivers rather than faffing about with uncompressed HDCP streams whether or not they are strongly encrypted.
"Our intention was rather to investigate the fundamental security of HDCP systems and to measure the actual financial outlay for a complete knockout," Güneysu explained, H Security reports. "The fact that we were able to achieve this in the context of a PhD thesis and using materials costing just €200 is not a ringing endorsement of the security of the current HDCP system." ®