Method of authenticating information, disk playback apparatus, and entertainment apparatus

A disk playback apparatus for playing back information on a disk-type recording medium, comprising:

• absolute authentication means for performing an absolute authentication process for authenticating a recording medium with information for authentication being recorded in a predetermined position therein, according to a first rule at a predetermined time, wherein said first rule is that normal authentication is declared in said absolute authentication process if the information for authentication is detected as being recorded in said predetermined position;
• executing means for executing a program transferred from said recording medium if normal authentication is declared in said absolute authenticating process;
• and
• arbitrary authentication means for performing an arbitrary authentication process for authenticating said disk playback apparatus according to a second rule at an arbitrary time while said program is executing, wherein said second rule is that normal authentication is declared in said arbitrary authentication process if the information for authentication is not detected in arbitrary positions other than said predetermined position,
• wherein said absolute authentication means comprises means for performing said absolute authentication process according to said first rule when said recording medium starts being accessed for the first time, and said arbitrary authentication means comprises means for performing said arbitrary authentication process according to said second rule at least once after said absolute authentication process.

An entertainment apparatus for performing processing operations using programs and data reproduced from a recording medium, comprising:

• absolute authentication means for performing an absolute authentication process for authenticating a recording medium with information for authentication being recorded in a predetermined position therein, according to a first rule at a predetermined time, wherein said first rule is that normal authentication is declared in said absolute authentication process if the information for authentication is detected as being recorded in said predetermined position;
• executing means for executing a program transferred from said recording medium if normal authentication is declared in said absolute authenticating process;
• and
• arbitrary authentication means for performing an arbitrary authentication process for authenticating said entertainment apparatus according to a second rule at an arbitrary time while said program is executing, wherein said second rule is that normal authentication is declared in said arbitrary authentication process if the information for authentication is not detected in arbitrary positions other than said predetermined positions,
• wherein said absolute authentication means comprises means for performing said absolute authentication process according to said first rule when said recording medium starts being accessed for the first time, and said arbitrary authentication means comprises means for performing said arbitrary authentication process according to said second rule at least once after said absolute authentication process.