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US 8,712,045 B2Granted
Digital rights management for media streams
AssigneeMicrosoft Corporation
InventorsKedarnath A. Dubhashi, Majd Bakar, Douglas Steedman
Life of this patent
Estimating the term…
Abstract
This document describes techniques and apparatuses enabling application of digital rights management (DRM) to media streams. In one embodiment, three license levels are used to protect numerous television channels without undue use of computing resources.
Claims16
A method comprising:
- encrypting, by a licensing server, using a public key of a public/private key pair and an asymmetric-key algorithm, a root license that includes a root key;
- encrypting, using the root key and a first symmetric-key algorithm, a media-stream license that includes a symmetric media-stream key;
- encrypting, using the symmetric media-stream key and a second symmetric-key algorithm, a leaf license that includes a content key, the leaf license provided in-band with content provided to a computing device;
- providing, by the licensing server and prior to providing content encrypted with the content key, the root license, the media-stream license, and the leaf license, the providing effective to enable the computing device having a private key of the public/private key pair and the content encrypted with the content key to decrypt the content;
- repeating the act of encrypting the root license after a first period, repeating the act of encrypting the media-stream license after a second period, and repeating the act of encrypting the leaf license after a third period, the first period longer than the second period, the second period longer than the third period;
- and
- limiting a loss of the decrypted content due to a single cryptographic compromise of one of the root license, the media-stream license, or the leaf license, the loss limited to an amount of the decrypted content lasting two times the second period.
4 more elements
A method comprising:
- receiving, by a computing device, a root license encrypted using a public key of a public/private key pair and including a root key;
- receiving a media-stream license encrypted using the root key and including a symmetric media-stream key;
- receiving a leaf license, in-band with content, having a content key, the leaf license encrypted using the symmetric media-stream key;
- receiving the content encrypted using the content key and prior to receiving the root license, the media-stream license, and the leaf license;
- decrypting, by the computing device, the root license using a private key of the public/private key pair to determine the root key;
- decrypting the media-stream license using the root key to determine the symmetric media-stream key;
- decrypting the leaf license using the symmetric media-stream key to determine the content key;
- decrypting the content using the content key to provide decrypted content;
- and
- repeating the acts of receiving the root license and decrypting the root license after a first period, repeating the acts of receiving and decrypting the media-stream license after a second period, and repeating the acts of receiving and decrypting the leaf license after a third period;
- and
- limiting a loss of the decrypted content due to a single cryptographic compromise of one of the root license, the media-stream license, or the leaf license, the loss limited to an amount of the decrypted content lasting two times the second period.
9 more elements
Dependencies are inferred from the claim text.