A signal (801) of a first code string made through replacing a part of a code string of a predetermined format with dummy data is sent to code string rewriting means (1802) via code string resolution means (1801). A signal (806) of a second code string for complementing the dummy data part in the signal (801) is sent to the code string rewriting means (1802) via control means (1805) and the dummy data in the first code string is rewritten to the second code string. At the time of trial viewing/listening, a signal (802) from the code string resolution means (1801) is selected by a switch (1808), and when the second code string (806) is acquired through content purchase, a signal (803) from the code string rewriting means (1802) is selected by the switch (1808). Thus, trial viewing/listening of a content such as music is made possible while the possibility of decryption is eliminated. By acquiring a relatively small quantity of data, reproduction of a high-quality content is made possible.