| 摘要 |
When manufactured, an optical data carrier is provided with digital information, which is written and stored in accordance with at least one previously defined encoding method for error correction and which may be read and decoded at a later stage by means of an optical reader with correction of errors in accordance with said encoding method. A predetermined number of logical symbols or bits are selected at predetermined positions in the digital information to be stored on the data carrier. A set of logical errors are intentionally created by replacing the selected symbols with corresponding symbols in a predetermined code sequence representing the identity of the data carrier. The logical errors are of such a type as to be normally corrected by the optical reader, when the data carrier is read and/or copied. The presence of at least a subset of the set of logical errors during reading without error correction of at least part of the digital information on the disc is interpreted as evidence of the data carrier having an identity determined by the set of logical errors. |
