| 摘要 |
A method for copy protecting a record carrier using a pattern of logical errors which cannot be corrected by the error correcting rules predefined for the record carrier. The pattern of logical errors represents access control information. The logical errors are generated during decoding the bit sequence read from the record carrier. Bit errors may be positioned in the bit sequence so as to counteract de-interleaving which is part of an error decoding process in a reading device and accumulate in error words which are uncorrectable. Also a method for detecting access control information and a retrieval arrangement, which detects the access control information by selecting at least one error location, but not all error locations on the record carrier, and verifying the presence of an error by reading the selected error location via the reading means.
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