Abstract: A content copying device has a mutual authentication section that performs a mutual authentication with a copy source recording medium and a copy destination recording medium respectively and generates a first medium unique key and a second medium unique key, a content key decrypting section that reads an encrypted content key from the copy source recording medium, and decrypts the encrypted content key using information based on the first medium unique key, a content key encrypting section that encrypts the decrypted content key using information based on the second medium unique key and writes the encrypted content key onto the copy destination recording medium, and a content copying section that reads an encrypted content from the copy source recording medium and writes the content onto the copy destination recording medium without performing decryption.

Abstract: A content copying device has a mutual authentication section that performs a mutual authentication with a copy source recording medium and a copy destination recording medium respectively and generates a first medium unique key and a second medium unique key, a content key decrypting section that reads an encrypted content key from the copy source recording medium, and decrypts the encrypted content key using information based on the first medium unique key, a content key encrypting section that encrypts the decrypted content key using information based on the second medium unique key and writes the encrypted content key onto the copy destination recording medium, and a content copying section that reads an encrypted content from the copy source recording medium and writes the content onto the copy destination recording medium without performing decryption.

Abstract: A recording device has a content encryption unit for writing a content encrypted with a content key in a recording medium, and a key encryption unit for encrypting the content key and writing the encrypted content key in the recording medium. A content key processing device has a key decryption unit that decrypts the content key that has been encrypted and recorded in a recording medium, and a key encryption unit that re-encrypts the decrypted content key with predetermined information and writes the re-encrypted content key in the recording medium.

Abstract: The present invention relates to an acoustic reproducing apparatus which is suitable particularly for listening to reproduced sound with noise through an open-air-type head phone. A sound leakage frequency band, when a head phone is loaded is measured in advance, and operation of a filter attenuating that sound leakage frequency band is changed-over. Thereby the sound leakage from the head phone to the outside in the loaded state is controlled. Also, a noise frequency characteristic is measured in advance, the low frequency band is intensified so as to correspond to that characteristic, and operation of the filter for attenuating the high frequency band containing the above-mentioned sound leakage frequency band is controlled to be changed-over.