INFORMATION PROCESSING METHOD, DECRYPTION METHOD, INFORMATION PROCESSING DEVICE, AND COMPUTER PROGRAM

摘要

There is provided an encrypted text providing configuration employing a tree structure based on the SD method and capable of reducing the information amount to be stored in a device for decrypting the encrypted text. Among labels corresponding to subsets set according to the SD method and the LSD method, an intermediate label is set which enables calculation of a label corresponding to a special subset. The other intermediate labels can be calculated by applying a one-direction replacement F having a trapdoor based on the value of one intermediate label. A receiver provides a label not corresponding to the special subset and one intermediate label. The receiver can calculate the other intermediate label by executing the one-direction replacement F having a trapdoor for the intermediate label held and calculate all the necessary labels.