Method for Distinguishing the Digital Images in Different Formats

Nowadays, the energy systems are considered to be the main vital factor for the functioning of society. Today, this part of the infrastructure cannot exist without the informative infrastructure, so it needs efficient information and cyber protection. To detect the data integrity violations is one of the main tasks in the field of information security. In the paper, the digital images are considered as information content. The image integrity violation often results in the change of the original storage format. The format change is an indicator of the image transformation. At the same time, this fact can be considered as an indirect indicator of its integrity violation. The effective method for distinguishing the original image in lossless format from the image re-saved to lossless format from lossy format is developed in the current work. The proposed method is an improvement of the method developed by the authors earlier. The method is based on the analysis of the number of non-intersecting image blocks, in which the normalized gap of maximum singular value increases due to the image's re-saving into a lossy format. The algorithmic implementation of the improved method allowed us to reduce the examination time in 38-56 times for more than 50% of images originally stored in lossy format compared to the prototype method. The algorithm efficiency was evaluated using Type I and Type II errors, as well as applying the accuracy coefficient (ACC). As a result of testing, Type I error was not detected, Type II error rate was 3.6%, ACC = 0.98. The obtained estimations are independent of the quality factor used when the image was initially saved in a lossy format. The developed algorithm is more efficient than almost all modern analogues, except for the prototype one. The theoretical basis of the proposed improved method makes it possible to use it for the study of the digital image integrity, violated by a minor disturbance, in particular for steganalysis in conditions of low capacity of the hidden communication channel