Abstract: The present invention provides a method performed on a computer of preventing re-use of compromised keys in a broadcast encryption system. In an exemplary embodiment, the method includes (1) incorporating a particular set of Sequence Keys assigned by a license agency into individual receivers, (2) assigning a Sequence Key Block (SKB) by the license agency to at least one distributed protected file, (3) performing incremental cryptographic testing by the individual receivers to determine if a selected Sequence Key from the set of Sequence Keys is compromised, (4) if the selected Sequence Key is not compromised, decrypting the file, and (5) if the selected Sequence Key is compromised and if a subsequent Sequence Key from the set of Sequence Keys is available, selecting the subsequent Sequence Key.

Abstract: Embodiments of the invention relate to obtaining forensic information for an anonymous attack of digital content without variations in a broadcast encryption system. In one embodiment a media device, being configured to record digital content on recordable media, receives digital content, a unified media key block, and a recording key table. The device calculates a set of recording keys from the recording key table using a media key variant from the unified media key block. The device then generates a title key and encrypts by the digital content in the generated title key. The device then encrypts the generated title key in each one of the calculated recording keys, adds a header including the encrypted titles keys to the encrypted digital content, and stores the encrypted digital content with the header on recordable media.

Abstract: According to one embodiment of the present invention, a system, method, and computer program product is provided for rebinding title keys in clusters of devices with distinct security levels in broadcast encryption systems. The method includes receiving a new management key and unbinding an encrypted title key with a previously used management key, the title key having a security class and residing in a title key block for a device having a security class, the device being in a cluster of devices including devices having a plurality of security classes. If the device security class is lower that the title key security class, the unbound title key is partially rebound with the new management key. the partially rebound title key is then saved in the title key block for the device.

Abstract: According to one embodiment of the present invention, a system, method, and computer program product is provided for rebinding title keys in clusters of devices with distinct security levels in broadcast encryption systems. The method includes receiving a new management key and unbinding an encrypted title key with a previously used management key, the title key having a security class and residing in a title key block for a device having a security class, the device being in a cluster of devices including devices having a plurality of security classes. If the device security class is lower that the title key security class, the unbound title key is partially rebound with the new management key. the partially rebound title key is then saved in the title key block for the device.

Abstract: According to one embodiment of the present invention, a method for protecting content in a broadcast-encryption-based system, where the devices in the system receive a recording key table. Each device generates a set of recording keys from the recording key table using a media key variant calculated from the broadcast encryption system's media key block. The digital content is encrypted in a title key picked by the recorder. The selected title key is also encrypted in each one of the recorder's generated recording keys. To play back the content, a player uses one of its generated recording keys to decrypt the title key and the decrypt the content. The recording key table is designed so that any two devices are guaranteed to have at least one key in common during normal operation, although during a forensic situation, this rule can be abandoned.

Abstract: A method for enforcing compliance in both the copy protect domain and service subscription domain for streamed multicast data. Each content is encrypted with a title key that itself is encrypted with a channel unique key which is a hash of a session key and a channel key. A compliant player is given the channel key upon registration for a subscription service (representing subscription protection) and is also given device keys upon activation (representing copy protection) for decrypting the session key. Consequently, the channel unique key can be obtained (and, hence, the content decrypted) only by a player that is compliant with both copy protection rules and subscription rules. The channel key can be refreshed periodically as subscriptions change or expire.

Abstract: Sets of encryption keys useful by devices for decrypting encrypted content are defined using an error-correcting code such as a Reed-Solomon code to define vectors of length “n” over an alphabet of (0, . . . , N?1), wherein “n” is the number of columns in a key matrix and “N” is the number of rows in the matrix. Each vector represents a set of keys that can be assigned to a device. With this invention, overlap between sets of keys can be minimized to minimize the possibility that the key set of an innocent device might be inadvertently revoked when the key set of a compromised device is revoked. Also, only the generating matrix of the error-correcting code and the index of one set of keys need be stored in memory, since all previously defined key sets can be regenerated if need be from just the generating matrix and index.

Abstract: A system for protecting content on recordable media for, e.g., DVD audio disks, flash memory media, or other media includes providing a media key block (MKB) on each media, with each MKB including 25,000 encryptions of a media key by 25,000 or so device keys. Each authorized player in the system has a single device key from among the system device keys with which to decrypt the media key. To avoid a coincidence attack in which a hacker can learn the MKB and associated media key and then guess at a device key without knowing its position in the MKB, the media key is XORed with a number representing each position in the MKB, and only then encrypted with the device key corresponding to that position.

Abstract: A system, method, business method, and computer program product for conducting electronic transactions with a potentially untrusted server while maintaining user anonymity and transaction privacy, yet allowing the server to verify the user is a valid subscriber entitled to participate in the transaction. Anonymous service requests are sent to the server. The server transmits responses that have been encrypted such that only valid subscribers can decrypt them. Broadcast encryption schemes that enable selective revocation of misbehaving subscribers will tip off requestors that the server is trying to identify them. Transaction and content quantity can be monitored for usage-based billing while maintaining anonymity. Each content item may be uniquely encrypted with a content key that is then encrypted by a session key and included in encrypted form with a response, to reduce the computational workload.

Abstract: Sets of encryption keys useful by devices for decrypting encrypted content are defined using an error-correcting code such as a Reed-Solomon code to define vectors of length “n” over an alphabet of (0, . . . , N−1), wherein “n” is the number of columns in a key matrix and “N” is the number of rows in the matrix. Each vector represents a set of keys that can be assigned to a device. With this invention, overlap between sets of keys can be minimized to minimize the possibility that the key set of an innocent device might be inadvertently revoked when the key set of a compromised device is revoked. Also, only the generating matrix of the error-correcting code and the index of one set of keys need be stored in memory, since all previously defined key sets can be regenerated if need be from just the generating matrix and index.

Abstract: A method for enforcing compliance in both the copy protect domain and service subscription domain for streamed multicast data. Each content is encrypted with a title key that itself is encrypted with a channel unique key which is a hash of a session key and a channel key. A compliant player is given the channel key upon registration for a subscription service (representing subscription protection) and is also given device keys upon activation (representing copy protection) for decrypting the session key. Consequently, the channel unique key can be obtained (and, hence, the content decrypted) only by a player that is compliant with both copy protection rules and subscription rules. The channel key can be refreshed periodically as subscriptions change or expire.

Abstract: A method of evaluating a tetrahedral linear interpolation function utilizes a table preparation process and a linear interpolating process. In the table preparation process, values v and domain points p of the function are related by two tetrahedral interpolation variables denoted as a matrix T and a vector t, as follows: v=t+pT. The coordinates of p include n components, and the value v includes m components. The matrix T includes n rows and m columns, as it must to relate p to v. If the value of the function is scalar, t is also a scalar, and T is a vector of n elements. From the coordinates of the (n+1) domain input points and the function values v at these points, the values of variables t and T are computed and stored in a table. The linear interpolation procedure of the invention uses the values tabulated for t and T to calculate an approximation for the components of the function value v at a given p.

Abstract: The invention provides approximation of the value of a function of three variables. The invention embraces three processes: function domain packing, polyhedron extraction, and volumetric interpolation. The processes are applied to a mathematical function to calculate an approximation for the function range output value at a point which has been arbitrarily selected from the input domain of the function. Function domain packing utilizes two interlocked domain subdivisions. A first subdivision and a second subdivision each divide the domain space into rectangular solids. Each subdivision is accomplished by means of a plurality of planes of constant value corresponding to each of the input dimensions. After a function domain has been so subdivided, a tetrahedral volume is extracted from the fraction domain space. This tetrahedral volume is defined by two points from the first subdivision and two points from the second subdivision.