A recording-playback system (300,1300) comprising a recording medium device (100,1100) and a recording-playback device (200,1200), wherein the recording medium device (100,1100) includes a tamper-resistant unit and a memory unit, wherein the tamper-resistant unit includes - an identification information storage subunit that stores therein identification information specific to the tamper-resistant unit, and - a certification subunit operable to generate certification information that certifies validity of the recording medium device (100, 1100) by digitally signing a random number received from the recording-playback device (200, 1200) and the identification information read from the identification information storage subunit, and to output the generated certification information, the memory unit includes an encrypted content storage subunit for storing therein an encrypted digital content, the recording-playback device (200, 1200) includes - a verification unit operable to acquire the certification information from the recording medium device (100, 1100), verify the validity of the recording medium device (100, 1100) according to the acquired certification information, and when the verification has failed, prohibit decrypting the encrypted digital content or encrypting a digital content, and - a content encryption-decryption unit operable, when the verification has succeeded, to encrypt, according to the identification information, the digital content and record the encrypted digital content in the encrypted content storage subunit, or to decrypt the encrypted digital content read from the encrypted content storage subunit according to the identification information, wherein the recording-playback system (300, 1300) is characterized by the memory unit further includes a center-issued value storage subunit that stores a value obtained from a center (600,1600), the tamper-resistant unit further includes - a vendor-issued value storage subunit that stores a value generated by a vendor which manufactures the tamper-resistant unit, - a generation subunit operable to generate the identification information specific to the tamper-resistant unit by using the value stored in the vendor-issued value storage subunit and the value stored in the center-issued value storage subunit, and wherein the identification information is a media ID identifying the recording medium device (100, 1100), and the value generated by the vendor which manufactures the tamper-resistant unit is a portion of the media ID, and the value obtained from the center is a remaining portion of the media ID. - an identification information storage subunit that stores therein identification information specific to the tamper-resistant unit, and - a certification subunit operable to generate certification information that certifies validity of the recording medium device (100, 1100) by digitally signing a random number received from the recording-playback device (200, 1200) and the identification information read from the identification information storage subunit, and to output the generated certification information, - a verification unit operable to acquire the certification information from the recording medium device (100, 1100), verify the validity of the recording medium device (100, 1100) according to the acquired certification information, and when the verification has failed, prohibit decrypting the encrypted digital content or encrypting a digital content, and - a content encryption-decryption unit operable, when the verification has succeeded, to encrypt, according to the identification information, the digital content and record the encrypted digital content in the encrypted content storage subunit, or to decrypt the encrypted digital content read from the encrypted content storage subunit according to the identification information, - a vendor-issued value storage subunit that stores a value generated by a vendor which manufactures the tamper-resistant unit, - a generation subunit operable to generate the identification information specific to the tamper-resistant unit by using the value stored in the vendor-issued value storage subunit and the value stored in the center-issued value storage subunit, and