Spatial models for localization of image tampering using distributed source codes

Media authentication is important in content delivery via untrusted intermediaries, such as peer-to-peer (P2P) file sharing. Many dif-ferently encoded versions of a media file might exist. Our previous work applied distributed source coding not only to distinguish the legitimate diversity of encoded images from tampering but also lo-calize the tampered regions in an image already deemed to be inau-thentic. An authentication decoder was supplied with a Slepian-Wolf encoded image projection as authentication data. A localization de-coder required only incremental localization data beyond the authen-tication data since we use rate-adaptive distributed source codes. We extend the localization decoder with 1D and 2D spatial mod-els to exploit the contiguity of the tampered regions. Our results show that the spatial decoders save 10 % to 17 % of authentication plus localization data size and offer greater confidence in tampering localization. Index Terms — image authentication, image tampering local-ization, distributed source coding 1