Information Hiding by Coverings *

We propose a formal model for embedding information in black-white images and prove the equivalence between existence of embedding schemes and covering codes. An asymptoticly tight bound on the performance of embedding schemes is given. We construct efficient embedding schemes via known coverings. In particular, one of those schemes allows to embed up to log 2 (n + 1) bits in coverwords of n bits, changing at most one bit, which is twice better than [6]. We rewrite some previous schemes with a look towards their covering structures. Finally, we address the problem of active warden in a similar way, giving a model, establishing the relationship with centered codes and concluding by a construction of schemes resisting to active warden.