Batch steganography in the real world

We examine the universal pooled steganalyzer of [15] in two respects. First, we confirm that the method is applicable to a number of different steganographic embedding methods. Second, we consider the converse problem of how to spread payload between multiple covers, by testing different payload allocation strategies against the universal steganalyzer. We focus on practical options which can be implemented without new software or expert knowledge, and we test on real-world data. Concentration of payload into the minimal number of covers is consistently the least detectable option. We present additional investigations which explain this phenomenon, uncovering a nonlinear relationship between embedding distortion and payload. We conjecture that this is an unavoidable consequence of blind steganalysis. This is significant for both batch steganography and pooled ste-ganalysis. Copyright 2012 ACM.