METHOD OF INTRODUCING SECRECY IMPROVEMENT BY USING ERROR CORRECTING CODE

摘要

[PROBLEMS TO BE SOLVED] In a recording medium or memory medium system with an error correcting function, when information is subjected to the coding, redundant information for the correction of errors is included. Because of it, even if a part of coded data on a recording medium or a memory medium is changed or omitted and if it is in a tolerable range of the system, its decoding can be correctively made. As a result, the system is strong against dart and easily recognizable. The secrecy of data, however, is not taken into consideration. Generally, in the improvement of the secrecy of information, a critical issue is a managing and maintaining method of independent information necessary for its system that, for instance, corresponds to encryption key information. [MEANS FOR SOLVING THE PROBLEMS] If independent information is such an amount or a modifying position that an error correcting function is not disturbed, it can be used as modifying information for a recording medium or a memory medium. Meanwhile, in the case where the independent information is coded, there may be parts that are consistent with a coded state before modifying. That is why it becomes difficult for the third party to specify an amount or a position of the independent information. As a result, thesecrecy of the independent information can be secured.