Information encryption device, information distribution device, control method thereof, computer program and computer readable storage medium

摘要

The present invention stores and manages only one piece of key information even if contents information includes a plurality of partial contents arranged in a sequence, and the partial contents are encrypted with different keys. When a piece of contents information includes four partial contents or divided into four partial contents, a key for each of four node positions is generated through four steps of operations from a key for the top root. Node keys P (i, 1) and P (i, i) at both sides are generated by a one-way function from node keys P (i−1, 1) and P (i−1, i−1) at the upper i−1th layer, and a node key P (i, m) (m=2, 3, . . . , i−1) are generated by a one-way function which can generate the keys from any of node keys P (i−1, m−1) and P (i−1, m) at the upper i−1th layer, where jth node key at the ith layer is represented as P (i, j) (j=1, 2, . . . , i−1). Then, each of partial contents is encrypted with key information generated at a terminal layer. If only a root key is saved, one encrypting key can be generated for a range of partial contents arranged in a sequence.