Even though Intel confirmed the legitimacy of the leaked HDCP key a few weeks ago, company representatives were adamant that software decryption remained unlikely.
Less than two weeks have passed, and now researchers from Stony Brook University in New York have developed code capable of decrypting 1080p video-streams in real-time on a mainstream PC.
According to authors Rob Johnson and Mikhail Rubnich, "the HDCP cipher is designed to be efficient when implemented in hardware, but it is terribly inefficient in software, primarily because it makes extensive use of bit operations. Our implementation uses bit-slicing to achieve high speeds by exploiting bit-level parallelism".
The result is that the decryption code, running as a single threaded application, can handle 181 VGA frames per second on a 2.33GHz Intel Xeon 5140 or 76 frames on a 2.53GHz Core 2 Duo P9600. Obviously a 1080p video-stream will be significantly more processor intensive. However, if parallelised across two cores, the researchers believe that a "high-end 64-bit CPU" with 1.6GB RAM could easily handle high-def video at 30fps.
Obviously, the code has been released purely in the name of science, "in hopes that it might be useful to other people researching or implementing the HDCP protocol". While Intel has threatened legal action to anyone making use of the master key, scientific and academic research often falls under the protection of the Digital Millennium Copyright Act (DMCA) safe harbours.
The decryption algorithm is still a work in progress, with optimisations such as SSE implementation being planned. The code has been released under an open source (BSD) license, though, so any intrepid programmers are welcome to poke around with it for themselves.
