Estimating JPEG2000 compression for image forensics using Benford's Law

Abstract

With the tremendous growth and usage of digital images nowadays, the integrity and authenticity of digital content is becoming increasingly important, and a growing concern to many government and commercial sectors. Image Forensics, based on a passive statistical analysis of the image data only, is an alternative approach to the active embedding of data associated with Digital Watermarking.Benford's Law was first introduced to analyse the probability distribution of the 1 st digit (1-9) numbers of natural data, and has since been applied to Accounting Forensics for detecting fraudulent income tax returns [9]. More recently, Benford's Law has been further applied to image processing and image forensics. For example, Fu et al. [5] proposed a Generalised Benford's Law technique for estimating the Quality Factor (QF) of JPEG compressed images. In our previous work, we proposed a framework incorporating the Generalised Benford's Law to accurately detect unknown JPEG compression rates of watermarked images in semi-fragile watermarking schemes. JPEG2000 (a relatively new image compression standard) offers higher compression rates and better image quality as compared to JPEG compression. In this paper, we propose the novel use of Benford's Law for estimating JPEG2000 compression for image forensics applications. By analysing the DWT coefficients and JPEG2000 compression on 1338 test images, the initial results indicate that the 1 st digit probability of DWT coefficients follow the Benford's Law. The unknown JPEG2000 compression rates of the image can also be derived, and proved with the help of a divergence factor, which shows the deviation between the probabilities and Benford's Law.Based on 1338 test images, the mean divergence for DWT coefficients is approximately 0.0016, which is lower than DCT coefficients at 0.0034. However, the mean divergence for JPEG2000 images compression rate at 0.1 is 0.0108, which is much higher than uncompressed DWT coefficients. This result clearly indicates a presence of compression in the image. Moreover, we compare the results of 1 st digit probability and divergence among JPEG2000 compression rates at 0.1, 0.3, 0.5 and 0.9. The initial results show that the expected difference among them could be used for further analysis to estimate the unknown JPEG2000 compression rates.

Countering anti-forensics to wavelet-based compression

“…Future research shall be devoted to a deeper study of the joint DWT histogram with a more comprehensive analysis than using the Hough transform, and to the compression rate estimation from (antiforensic) wavelet-based compressed images with comparisons to the JPEG2000 estimation method [21]. Moreover, the proposed forensic method will also be tested on other image datasets besides UCID-v2 [18], considering other wavelet-based compression algorithms besides JPEG2000 and SPIHT.…”

An enhanced feature set for pattern recognition based contrast enhancement of contact-less captured latent fingerprints in digitized crime scene forensics

“…Benford's law Distribution of most significant digits within a block (similar to 18 for the DCT-coefficients of a JPEG compression) 1 show a significant improvement of the performance of the pattern recognition based contrast enhancement approach. In particular, a half total error rate (HTER) of 7.3% is achieved for the cooperative white furniture surface.…”

An improved watermarking algorithm using adaptive threshold

“…Mild JPEG2000 compression is also considered as non-malicious manipulation. In another related work [8], we only discussed the wavelet coefficients obeyed the Benford's law, but not incorporated in the semi-fragile watermarking filed. Therefore, we continue to discuss the relationship between the threshold and the compression ratio (CR) of JPEG2000 for improving the accuracy of detection in this paper.…”