Patent ID: 7376073

Claim:
A method for determining authenticity of an optical medium comprising: modifying an optical path of the optical medium, the optical medium including a first layer adjacent a data layer, the modifying of the optical path of the optical medium comprising: selecting a region of the first layer to be distorted; and prior to a reading operation of the medium, distorting the region of the first layer, the distorted region extending in a direction along a track of the data layer; performing a reading operation of the optical medium, the distorted region modifying the reading operation of data stored in the data layer corresponding to the distorted region, such that when data stored in the data layer corresponding to the distorted region is read, a measurable change in system performance of the reading operation results and the ability to perform the reading operation in the distorted region is maintained with at least one of error-free status and degrees of error status that indicates an avoidance of complete data corruption while slowing down the reading operation process, the distorted region maintaining its optical characteristics following irradiation of the distorted region during the reading operation; detecting the measurable change in system performance that occurs during the reading operation that is maintained during reading of the distorted region, wherein the measurable change in system performance is based on timing of the reading operation; authenticating the optical medium based on the measurable change in the system performance.