  It is known that JPEG images uploaded to social networks (SNs) are mostly
re-compressed by the social network providers. Because of such a situation, a
new image identification scheme for double-compressed JPEG images is proposed
in this paper. The aim is to detect single-compressed images that have the same
original image as that of a double-compressed one. In the proposed scheme, the
signs of only DC coefficients in DCT coefficients and one threshold value are
used for the identification. The use of them allows us to robustly avoid errors
caused by double-compression, which are not considered in conventional schemes.
The proposed scheme has applications not only to find uploaded images
corresponding to double-compressed ones, but also to detect some image
integrity. The simulation results demonstrate that the proposed one outperforms
conventional ones including state-of-art image hashing one in terms of the
querying performance.
