This paper introduces a novel compatibility attack to detect a steganographic message embedded in the DCT domain of a JPEG image at high-quality factors (close to 100). Because the JPEG compression is not a surjective function, i.e. not every DCT blocks can be mapped from a pixel block, embedding a message in the DCT domain can create incompatible blocks. We propose a method to find such a block, which directly proves that a block has been modified during the embedding. This theoretical method provides many advantages such as being completely independent to Cover Source Mismatch, having good detection power, and perfect reliability since false alarms are impossible as soon as incompatible blocks are found. We show that finding an incompatible block is equivalent to proving the infeasibility of an Integer Linear Programming problem. However, solving such a problem requires considerable computational power and has not been reached for 8x8 blocks. Instead, a timing attack approach is presented to perform steganalysis without potentially any false alarms for large computing power.

翻译：本文提出了一种新型兼容性攻击方法，用于检测高质量因子（接近100）下JPEG图像DCT域中嵌入的隐写消息。由于JPEG压缩并非满射函数（即并非所有DCT块都能由像素块映射得来），在DCT域中嵌入消息可能产生不兼容块。我们提出了一种定位此类块的方法，该方法可直接证明某一块在嵌入过程中已被修改。这一理论方法具备诸多优势：完全独立于载体源失配问题、检测能力优异，且具备完美可靠性——一旦发现不兼容块，绝无虚警可能。研究表明，判定不兼容块等价于证明整数线性规划问题不可行。然而，求解此类问题需要巨大计算资源，且目前尚未能对8×8块实现求解。为此，我们提出了一种时序攻击方法，在具备强大计算能力时，可实现在无虚警前提下的隐写分析。