Efficient revocation of receivers
AssigneeSony Corporation
InventorTomoyuki Asano
Life of this patent
Estimating the term…
Abstract
Methods and apparatus for efficient revocation of receivers. In one implementation, a method of broadcast encryption includes: assigning a respective master key to each of a plurality of receivers, where each master key can be used to derive two or more of a plurality of sub keys; revoking one or more receivers, leaving one or more unrevoked receivers; for each master key of an unrevoked receiver, selecting the sub key that can be derived by that master key and derived by the most other master keys but not derived by a master key of any of the one or more revoked receivers; for each selected sub key, encrypting one ciphertext using that selected sub key; and sending the encrypted ciphertexts to the plurality of receivers.
Claims87
A method of broadcast encryption, comprising:
- assigning a respective master key to each of a plurality of receivers, where each master key can be used to derive two or more of a plurality of sub keys;
- revoking one or more receivers, leaving one or more unrevoked receivers;
- for each master key of an unrevoked receiver, selecting the sub key that can be derived by that master key and derived by the most other master keys but not derived by a master key of any of the one or more revoked receivers;
- for each selected sub key, encrypting one ciphertext using that selected sub key;
- and
- sending the encrypted ciphertexts to the plurality of receivers.
A method of broadcast decryption, comprising:
- receiving a ciphertext at a receiver;
- receiving a representation code at the receiver;
- selecting a target sub key from among a plurality of sub keys that can be derived from a master key stored at the receiver according to the received representation code;
- deriving the selected target sub key from the master key;
- and
- decrypting the received ciphertext using the derived sub key.
A method of encryption, comprising:
- defining a table having A rows and B columns;
- selecting a respective sub key for each element in the table, such that each element has a corresponding sub key;
- encrypting a media key using each sub key;
- storing each encrypted media key as the element in the table corresponding to the sub key used to encrypt that encrypted media key;
- providing the table to each of a plurality of receivers;
- and
- providing a master key to each of a plurality of receivers, where each master key can be used to derive two or more sub keys, including a sub key for a corresponding element in each column of the table.
A receiver for a broadcast encryption system, comprising:
- a storage device;
- a secure storage device storing a master key, where a plurality of sub keys can be derived from the master key;
- an input/output interface for receiving a ciphertext and a representation code;
- and
- a controller;
- where the controller is configured to:
- select a target sub key from among the plurality of sub keys that can be derived from the master key according to the received representation code;
- derive the selected target sub key from the master key;
- and decrypt the received ciphertext using the derived sub key.
A system for broadcast encryption, comprising:
- means for assigning a respective master key to each of a plurality of receivers, where each master key can be used to derive two or more of a plurality of sub keys;
- means for revoking one or more receivers, leaving one or more unrevoked receivers;
- means for selecting for each master key of an unrevoked receiver the sub key that can be derived by that master key and derived by the most other master keys but not derived by a master key of any of the one or more revoked receivers;
- means for encrypting for each selected sub key one ciphertext using that selected sub key;
- and
- means for sending the encrypted ciphertexts to the plurality of receivers.
A system for broadcast decryption, comprising:
- means for receiving a ciphertext at a receiver;
- means for receiving a representation code at the receiver;
- means for selecting a target sub key from among a plurality of sub keys that can be derived from a master key stored at the receiver according to the received representation code;
- means for deriving the selected target sub key from the master key;
- and means for decrypting the received ciphertext using the derived sub key.
A method of manufacturing data media, comprising:
- receiving an article of data media;
- recording a representation code on the article of data media, where the representation code indicates which of a plurality of sub keys are to be used for decryption;
- for each of the sub keys indicated by the representation code, encrypting a content key using that sub key, generating a respective encrypted content key for each indicated sub key;
- storing each of the encrypted content keys on the article of data media.
A manufacturing device for manufacturing data media, comprising:
- a storage device;
- an input/output interface;
- and
- a controller;
- where the controller is configured to:
- store a representation code on the article of data media, where the representation code indicates which of a plurality of sub keys are to be used for decryption;
- encrypt for each of the sub keys indicated by the representation code a content key using that sub key, generating a respective encrypted content key for each indicated sub key;
- store each of the encrypted content keys on the article of data media.
A method of broadcast encryption, comprising:
- assigning a respective master key to each of a plurality of receivers, where each master key can be used to derive two or more of a plurality of sub keys;
- revoking zero or more receivers, leaving one or more unrevoked receivers;
- for each master key of an unrevoked receiver, selecting the sub key that can be derived by that master key and derived by the most other master keys but not derived by a master key of any of the zero or more revoked receivers;
- for each selected sub key, encrypting one ciphertext using that selected sub key;
- and sending the encrypted ciphertexts to the plurality of receivers.
Dependencies are inferred from the claim text.