| 摘要 |
<p>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.</p> |
