Abstract: In view of the data security problems in the application of ENC, combined with the integrity certification requirements of CRC checksums under S-57 standard, a zero watermark algorithm for ENC is proposed which takes into account the characteristics of point tampering. Based on the analysis of the distribution law of the discrete point coordinate data represented by longitude and latitude in the ENC object standard (element), the algorithm constructs the generation model of the longitude-latitude check code, and combines the number of the discrete point to carry out the binary tree block processing of the ENC cell network, and solves the binary sequence based on the longitude-latitude check code of the discrete point by block column and scrambled encrypted watermark image are XOR operation to construct zero watermark image. In the algorithm, the introduction of the grid block technology and longitude-latitude check code can ensure the accuracy of ENC data and meet the CRC check sum, and it has the characteristics of point tampering location. Experimental results show that the watermark algorithm has good robustness, invisibility and a certain degree of tampering positioning accuracy, which is suitable for copyright protection of ENC.

Key words: check code, electric navigational chart, zero-watermark, arnold, tampering localization