Abstract: A method and system is disclosed for purposefully modifying the accessibility of information encoded upon an optical medium for indicating a state or history of the optical medium and/or a state or history of an item associated therewith. In one embodiment, the optical medium is purposefully damaged when the information is initially accessed so that upon subsequent access attempts of the information on the optical medium, a previous access of the information is detected by the purposefully induced errors. Thus, there is provided an effective technique for limiting illegal duplication and/or use of, e.g., software, movies, and music on compact disks and digital versatile disks. The present invention provides verification of persons and/or financial transaction cards during financial transactions. In another embodiment, a compact data storage device is disclosed having the approximate dimensions of a credit card that is capable of storing large amounts of data (e.g., 50-100 Megabytes).

Abstract: Methods for manufacturing optical discs with purposefully provided errors therein are disclosed, wherein the error instances can be used to identify the authenticity of the optical disc. Additionally, methods for determining the authenticity of an optical disc are disclosed, wherein values derived from descriptors of errors found on the disc are compared with corresponding known values indicative of an authentic disc for determining whether the disc was legitimately manufactured or not. Such methods may utilize errors that are correctable, uncorrectable, trackable, and/or untrackable. An end user (or the end user's optical reading laser) may be instructed to purposefully alter a portion of the disc in a predetermined manner so that an unauthorized copy of the disc is easily discoverable by, e.g., activation of an authentication program on the disc or accessible via a network such as the Internet.