Even though data transmitted between a data processing apparatus and disc recording and/or reproducing apparatus is monitored, copying the data is effectively prevented and the data can be protected. A write ID generator 20 of a disc recording and/or reproducing apparatus 10 generates independent write ID for each recording of data, and transmits the write ID to an encryptor 102 of a data processing apparatus 100. The encryptor 102 encrypts contents ID to be used for key information for encrypted contents data and data control information to restrict or prohibit copy by the use of an encrypting key based on the write ID. The encrypted data are transmitted to an encryptor 24 of the disc recording and/or reproducing apparatus 10 via an I/F 101 and I/F 19, and encrypted along with the write ID by the use of an encrypting key based on disc ID, and recorded to a disc 30.