Abstract: Content data is judged to determine whether data prepared by a digital device were altered by performing an authentication process using a medium on which content data are recorded; reading the content data from the medium; embedding, in the content data, data for verifying the pertinent content; extracting, from the content data, the data for verifying the pertinent contents; using the results of the extraction to determine whether the content data were altered. Preferably, the means includes means for identifying any portion containing altered data.

Abstract: A coding process for a facsimile transmission system employs block coding and dither matrices of black and white picture elements, wherein each matrix represents a portion of a subject. The subject is scanned to provide gray-scale tone-level data, and the data of continuous tone regions of the subject is represented by standardized patterns in matrix form. A run of identical patterns is counted in the scanning direction and a symbol indicating the number of such repetitions is placed in the code in lieu of the succession of code words representing individual ones of the repeating patterns. A second symbol is inserted into the code to indicate a succession of runs of repeating patterns in the same column now positioned in two or more rows. The second symbol is utilized in lieu of a repetition of code words corresponding to each of the repeated patterns.