A random-number generator generates first and second title keys on the basis of random numbers. A first DES encryption circuit for the title encrypts input data with the first title key. Initial values of this item of input data are a data identifier (ID) and program clock reference (PCR) that are extracted from a packet header. After completing the encryption of the initial values, a result of an encryption by a second DES encryption circuit for title serves as the input data for the first DES encryption circuit for title. The second DES encryption circuit for title encrypts a value of result of the encryption by the first DES encryption circuit for title with the second title key. An exclusive OR circuit outputs an exclusive OR of the data stored in the packet and a value of result of the encryption by the second DES encryption circuit for title. This exclusive OR turns out encrypted data.