To provide an information processing apparatus and a method thereof capable of reducing calculation processing for calculating a node key corresponding to each of nodes on a path from a root to the leaf to which its own device belongs to, in processing of providing encryption data such as a key of cryptograph to which a hierarchical tree structure is applied.
The encryption data providing processing to which the hierarchical tree structure is applied has a structure in which trap-door one-way permutation Fi and reverse permutation F-1i are applied to calculation processing and setting processing of each of the nodes in an a-branch tree (HKT), and execution of the trap-door one-way permutation Fi by the number of times equivalent to the length of the height of a tree at the maximum can complete node key calculation in the calculation of a node key in each device. By repeating execution of the trap-door one-way permutation Fi by using a key held in the device, the node key in an upper node can be sequentially calculated.
Eiji Yamada
Toshio Sawada
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