| 摘要 |
PROBLEM TO BE SOLVED: To secure immunity against a conspiracy attack, and to shorten key lengths of encryption keys corresponding to hierarchies of respective scalabilities. SOLUTION: An encryption key (K<SB>2, 2</SB>) corresponding to bottom-hierarchy data of hierarchical scalabilities (R, L) is divided as a master key by the number of hierarchies of the scalability (R). To key element matrixes (M1 to M3) generated for each of the divided keys (e<SB>R2</SB>, e<SB>R1</SB>, e<SB>R3</SB>), arithmetic data obtained one after another by repeating a hash operation using a unidirectional hash function are allocated so that the hierarchy of the scalability (L) is held. Key elements having matching coordinates among the key matrixes (M1 to M3) are combined to generate partial keys (K<SB>1, 1</SB>to K<SB>2, 2</SB>) corresponding to the respective hierarchies of the scalabilities (R, L). COPYRIGHT: (C)2009,JPO&INPIT
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