1,715 research outputs found
On the Gold Standard for Security of Universal Steganography
While symmetric-key steganography is quite well understood both in the
information-theoretic and in the computational setting, many fundamental
questions about its public-key counterpart resist persistent attempts to solve
them. The computational model for public-key steganography was proposed by von
Ahn and Hopper in EUROCRYPT 2004. At TCC 2005, Backes and Cachin gave the first
universal public-key stegosystem - i.e. one that works on all channels -
achieving security against replayable chosen-covertext attacks (SS-RCCA) and
asked whether security against non-replayable chosen-covertext attacks (SS-CCA)
is achievable. Later, Hopper (ICALP 2005) provided such a stegosystem for every
efficiently sampleable channel, but did not achieve universality. He posed the
question whether universality and SS-CCA-security can be achieved
simultaneously. No progress on this question has been achieved since more than
a decade. In our work we solve Hopper's problem in a somehow complete manner:
As our main positive result we design an SS-CCA-secure stegosystem that works
for every memoryless channel. On the other hand, we prove that this result is
the best possible in the context of universal steganography. We provide a
family of 0-memoryless channels - where the already sent documents have only
marginal influence on the current distribution - and prove that no
SS-CCA-secure steganography for this family exists in the standard
non-look-ahead model.Comment: EUROCRYPT 2018, llncs styl
- …