(Semantic Security and Pseudo-Random Permutations)

Probabilistic symmetric encryption have already been widely studied, from a theoretical point of view. Nevertheless, many applications require length-preserving encryption, to be patched at a minimal cost to include privacy without modifying the format (e.g. encrypted lesystems). In this paper, we thus consider the security notions for length-preserving, deterministic and symmetric encryption schemes, also termed ciphers: semantic security under lunchtime and challenge-adaptive adversaries. We fur- thermore provide some relations for this notion between dieren t models of adversaries, and the more classical security notions for ciphers: pseudo-random permutations (PRP) and super pseudo-random permutations (SPRP).