Chaos-based crypto and joint crypto-compression systems for images and videos

Abstract

The security of image and video data is important for many applications which require in real-time a high security level. In the first part of this work, four chaos-based cryptosystems, flexible, efficient, and more robust against cryptanalysis, are designed and realized. The first two cryptosystems are based on the substitution-permutation network. The substitution is achieved by a proposed modified Finite Skew Tent Map (FSTM) to overcome various problems: fixed point, key space restriction, and limitation of mapping between plaintext and ciphertext. The third cryptosystem is a new and efficient structure. It is based on a binary diffusion layer of pixels, followed by a bit-permutation layer. The permutation is achieved by an efficient proposed formulation of the 2-D cat map. The fourth cryptosystem is faster than the others, having a very high security level. The confusion and the diffusion are performed in a single scan. Its design is based on a partial cryptanalysis that we performed on the Zhang algorithm. In the second part, two fast and secure selective chaos-based crypto-compressions are designed and realized to secure the High Efficiency Video Coding (HEVC) and its scalable version. In the first crypto-compression, a new algorithm is proposed to define the encryptable bits in the bit stream of the HEVC and the SHVC systems. The proposed solution encrypts a set of sensitive SHVC parameters at the entropy encoder (CABAC), while preserving all SHVC functionalities. Based on the tile concept, the second proposed crypto-compression provides protection of the ROI defined in the standard HEVC.