Steve and the Boyz reckon they’ve found a way to use DRM on P2P networks to distribute commercial media online.
It “works like a standard torrent network,” says Cryptopatents. When a user wants the content, “his machine grabs a list of the nearest peers and what parts of the content they have,” it says, going on, “The user downloads the individual pieces and the file is reassembled on his computer.”
But, Microsoft’s twist is to lock each packet using “several layers of encryption: public key cryptography, DES and RC4 for the algorithm’s different components,” says the story, going on >>>
In an ideal setting, the scheme works like this: Microsoft sends you a master key that has been enciphered with your public key. You decrypt the master key and the result is hashed using SHA. The output is split in two, with the first part used as the root of the machine authentication code key (MAC, similar to a checksum), the second is the DES key. The DES key is used to decrypt the RC4 content key that, in turn, is used to decrypt the content payload. The whole thing is XOR’d with the MAC and the output is reassembled for your viewing pleasure.
Under “Digital rights management scheme for an on-demand distributed streaming system,” and listing Jin Li and Yi Cui as the inventors, the Microsoft P2P DRM “may be optionally invoked by the owner,” says the abstract to patent application 10934823, adding >>>
With the DRM protection turned on, the media is encrypted before it is distributed in a P2P network, and is decrypted prior to its use (play back). The peers may still efficiently distribute and serve without authorization from the owner. Nevertheless, when the media is used (played back), the client node must seek proper authorization from the owner. The invention further provides a hierarchical DRM scheme wherein each packet of the media is associated with a different protection level. In the hierarchical DRM scheme of the invention there is usually an order of the protection level. As a result, in one embodiment of the invention, the decryption key of a lower protection layer is the hash of the decryption key at the higher protection level. That way, a user granted access to the high protection layer may simply hold a single license of that layer, and obtain decryption keys of that layer and below. The invention further provides for a process for managing digital rights to a scalable media file wherein a different encryption/decryption key is used to encrypt each truncatable media packet with a base layer without requiring additional storage space to store the key.
DRM is a dead horse. But they never give up, do they?
..… and identi.ca
First they ignore you, then they laugh at you, then they fight you, then you win ~ Mahatma Gandhi
Cryptopatents – Microsoft Patents P2P DRM Methods, January 4, 2010
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