Block convergence in repeated transform coding: JPEG-100 forensics, carbon dating, and tamper detection

Repeated rounding of sample blocks in alternating domains creates complex convergence paths. We study convergence and block stability for JPEG images compressed with quality factor 100 and derive methods to detect such compression in grayscale bitmap images, to estimate the number of recompressions, to identify the DCT implementation used for compression, and to uncover local tampering if image parts have been compressed with JPEG-100 at least once.