Patent ID: 7403924

Claim:
A communication terminal, comprising: an electronic value storage unit of the communication terminal, said storage unit configured to store an electronic value used in acquisition of book data containing a plurality of book data units corresponding to individual pages, along with a second decryption key used in decryption of at least one of a plurality of first decryption keys which are configured to decrypt the plurality of book data units, wherein said first and second decryption keys are different from each other; an electronic book request transmitter configured to transmit an electronic book readout request to read out a specific page to an electronic book providing server; a book data receiver configured to receive the book data and the plurality of first decryption keys from the providing server; a deductor configured to deduct an electronic worth from the electronic value storage unit of the terminal, corresponding to the specific page requested to be read out by the readout request; a first decryption key decryptor configured to decrypt the plurality of first decryption keys in increments of one first decryption key by use of a second decryption key, where said decryptor decrypts after a deduction by the deductor of the electronic worth corresponding to the specific page is completed; and a book data decryptor configured to decrypt the plurality of book data units, in increments of one book data unit, by use of a corresponding first decryption key decrypted by the first decryption key decryptor in conjunction with a deduction of the electronic worth.