Paper 2003/231

Public-Key Steganography with Active Attacks

Michael Backes and Christian Cachin

Abstract

A complexity-theoretic model for public-key steganography with active attacks is introduced. The notion of steganographic security against adaptive chosen-covertext attacks (SS-CCA) and a relaxation called steganographic security against publicly-detectable replayable adaptive chosen-covertext attacks (SS-PDR-CCA) are formalized. These notions are closely related to CCA-security and PDR-CCA-security for public-key cryptosystems. In particular, it is shown that any SS-(PDR-)CCA stegosystem is a (PDR-)CCA-secure public-key cryptosystem and that an SS-PDR-CCA stegosystem can be realized from any PDR-CCA-secure public-key cryptosystem with pseudorandom ciphertexts.