Magnetic recording medium authentication method, magnetic recording medium authentication system, and authenticable magnetic recording medium

Disclosed is a method of authenticating a magnetic recording medium, capable of immediately detecting unauthorized use of a magnetic recording medium by a stranger other than an owner of the magnetic recording medium, and maintaining a degree of compatibility with conventional magnetic recording mediums. In this method, a physical pattern is formed in a recording region adapted to magnetically record basic information thereon, so as to change a magnetic property of the recording region to an extent allowing the basic information to be read from and/or written in the recording region. On the occasion of authentication of the magnetic recording medium, a magnetic characteristic induced by the physical pattern is read from the recording region to generate authentication information in accordance with the magnetic characteristic. Then, the magnetic recording medium is authenticated in accordance with the authentication information. When the basic information on the magnetic recording medium formed with the physical pattern is duly rewritten, new authentication information is re-generated to authenticate the rewritten magnetic recording medium in accordance with the new authentication information.