Patent ID: 8634553

Claim:
An encryption key generating apparatus, applied to a communication system offering a delivery service of digital data with two or more types of hierarchical scalabilities, for generating an encryption key used in coding and decoding of the digital data, the encryption key generating apparatus comprising: input means for inputting an encryption key used in coding and decoding of a data unit in hierarchies at a lowest position out of hierarchies satisfying a service level allowed by the communication system, in each of first and second scalabilities selected from the two or more types of scalabilities; non-transitory storage means for storing, as a master key, the encryption key inputted by the input means; key dividing means for dividing the master key read out from the storage means, by a number of hierarchies in the first scalability set as a reference scalability out of the first and second scalabilities, to generate split keys corresponding to the respective hierarchies in the first scalability; matrix generating means, concerning a key element matrix generated based on one split key out of the split keys generated by the key dividing means, for assigning operation data successively obtained by repeating a hash operation on the one split key using a one-way hash function, at least to coordinate entries corresponding to respective hierarchies from the lowest hierarchy to the highest hierarchy in the second scalability in a hierarchy in the first scalability corresponding to the one split key, so as to generate key element matrices as coordinate representations of hierarchical values in the first and second scalabilities, for the respective hierarchies in the first scalability; key generating means for combining key elements coordinately consistent among the key element matrices generated by the matrix generating means, to generate partial keys corresponding to data units in the respective hierarchies in the first and second scalabilities; and output means for outputting the partial keys generated by the key generating means to a device for executing at least one of coding and decoding of the digital data.