Patent ID: 6934847
Filing Date: 2005-08-23
Classification: G06F,G11B

Abstract:
1. A data alteration checking apparatus for discriminating whether data recorded on a recording medium has been altered or not, comprising: reading means for respectively reading out a data block and a file from said recording medium on which with respect to one or each of a plurality of files belonging to a directory serving as an upper concept in which one or a plurality of files are bound, the data block including one or a plurality of list-type data structures each including a plurality of first arithmetic operation values which were arithmetically operated every said file on the basis of attribute information of the file by a predetermined arithmetic operating method which uses a unidirectional function and an original value cannot be obtained by performing a reverse arithmetic operation from a MAC value has been recorded into an area that is not accessed by a file system on said recording medium and each of said first arithmetic operation values has been written into the corresponding file; and comparing means for comparing a second arithmetic operation value which was arithmetically operated by said predetermined arithmetic operating method on the basis of the attribute information of said file read out by said reading means with said first arithmetic operation value which corresponds to said file and is included in said list-type data structure corresponding to said directory to which said file read out by said reading means belongs in said data block read out by said reading means, wherein on the basis of a result of the comparison by said comparing means, when said first and second arithmetic operation values do not coincide, it is determined that said file has been altered.