Tamper-evident Image using JPEG Fixed Points
This addresses the problem of image authentication for users needing to detect tampering, but it is incremental as it builds on known JPEG fixed-point phenomena.
The paper proves the existence of fixed points in JPEG compression and decompression, which can be reached within a few iterations while preserving visual quality, and uses this to develop a tamper-evident image method that exposes tampering by showing deviations from the fixed point image.
An intriguing phenomenon about JPEG compression has been observed since two decades ago- after repeating JPEG compression and decompression, it leads to a stable image that does not change anymore, which is a fixed point. In this work, we prove the existence of fixed points in the essential JPEG procedures. We analyze JPEG compression and decompression processes, revealing the existence of fixed points that can be reached within a few iterations. These fixed points are diverse and preserve the image's visual quality, ensuring minimal distortion. This result is used to develop a method to create a tamper-evident image from the original authentic image, which can expose tampering operations by showing deviations from the fixed point image.