A well-respected cryptographer claims he has discovered a way to break an Intel-backed format for encoding video transmissions - but is prevented by US law on speaking on the issue.
Niels Ferguson believes he could be prosecuted under the Digital Millennium Copyright Act (DMCA) so he has held off publishing his findings which suggest flaws with the High-bandwidth Digital Content Protection (HDCP) system.
Even though he lives in Holland, Ferguson fears that in the wake of the prosecution of Russian programmer Dmitry Sklyarov that the DMCA threatens freedom of speech throughout the world. Intel has not threatened him in any way but he still fears that the motion picture industry or some other body might still prosecute him.
Ferguson, who travels periodically to the States on business, told The Register that lawyers from the Electronic Frontier Foundation advised him he might still be liable to prosecution even if he published a paper in Holland.
All he is willing (or able) to say is that it would be possible to recover a master key for the encryption scheme in about two weeks.
"An experienced IT person can recover the HDCP master key in about two weeks using four computers and 50 HDCP displays," said Ferguson. "Once you know the master key, you can decrypt any movie, impersonate any HDCP device, and even create new HDCP devices that will work with the 'official' ones."
"This is really, really bad news for a security system," he said.
HDCP encrypts video on the DVI interface, which connects digital video cameras and DVD players with digital TVs and the like, and is designed to prevent illegal copying of video contents by encrypting the signal. It is expected to become widely available in hardware due out in the first quarter of next year but it is still not too late to mitigate problems he has found with HDCP.
Ferguson says the scheme is "fatally flawed" and he is not alone in his criticism. Other security researchers Scott Crosby and Kevin Irwin have gone one step further than Ferguson and published criticisms of the algorithm, and suggested ways to attack HDCP.
Intel has publicly downplayed the significance of the research and said none of the reported ways of breaking the scheme have been successful.
Clearly there's a need for further research. But this, as Ferguson points out, is been stymied by the DMCA. This law undermines the tradition of open analysis of encryption schemes that is needed for security. This story will run and run...®
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