PURPOSE: To control transmission data by a simple constitution without depending on the update time of a work key.

CONSTITUTION: Related information is decoded by using the work key taken out from a work key register 39 and a scramble key the identification data of data are taken out, in a decoding circuit 37. A download propriety decision circuit 43 reads the contract contents and the download possible number from the contract contents register 44 and the download possible number register 45 of a security module 46, respectively, and compares them. When it is decided that the contents of data is the data of decode possible multimedia newspaper and the download possible number is not 0, a data scramble key is rightly taken out from the decoding circuit 37 and the key is added to a PN generator 41 by turning on an ON/OFF switch circuit 42.