They also said the Blom's scheme key swap could be broken by a so-called conspiracy attack: obtaining the keys of at least 40 devices and reconstructing the secret symmetrical master matrix that was used to compute them.
Around the same time, Niels Ferguson independently claimed to have broken the HDCP scheme, but he did not publish his research, citing legal concerns arising from the controversial Digital Millennium Copyright Act.
In November 2011 Professor Tim Güneysu of Ruhr-Universität Bochum revealed he had broken the HDCP 1.3 encryption standard.
For each set of values, a special public key called a KSV (Key Selection Vector) is created.Each KSV consists of 40 bits (one bit for each HDCP key), with 20 bits set to 0 and 20 bits set to 1.It may perform some signal processing, such as upconverting video into a higher-resolution format, or splitting out the audio portion of the signal. Examples include home theater audio-visual receivers that separate and amplify the audio signal, while re-transmitting the video for display on a TV.A repeater could also simply send the input data stream to multiple outputs for simultaneous display on several screens.On September 16, Intel confirmed that the code had been cracked.
The attack used the fact that the pairing process sends the Km key obfuscated with an XOR.
by non-HDCP digital audio outputs (analog audio outputs have no quality limits).
Cryptanalysis researchers demonstrated flaws in HDCP as early as 2010.
This master key would neutralize the key revocation feature of HDCP, because new keys can be created when old ones are revoked.
Since the master key is known, it follows that an unlicensed HDCP decoding device could simply use the master key to dynamically generate new keys on the fly, making revocation impossible.
The FCC's Broadcast flag regulations, which were struck down by the United States Court of Appeals for the District of Columbia Circuit, would have required DRM technologies on all digital outputs from HDTV signal demodulators.