The ALASKA Steganalysis Challenge - A First Step Towards Steganalysis.

This paper presents ins and outs of the ALASKA challenge, a steganalysis challenge built to reflect the constraints of a forensic steganalyst. We motivate and explain the main differences w.r.t. the BOSS challenge (2010), specifically the use of a ranking metric prescribing high false positive rates, the analysis of a large diversity of different image sources and the use of a collection of steganographic schemes adapted to handle color JPEGs. The core of the challenge is also described, this includes the RAW image data-set, the implementations used to generate cover images and the specificities of the embedding schemes. The very first outcomes of the challenge are then presented, and the impacts of different parameters such as demosaicking, filtering, image size, JPEG quality factors and cover-source mismatch are analyzed. Eventually, conclusions are presented, highlighting positive and negative points together with future directions for the next challenges in practical steganalysis.