Efficient and secure cipher scheme for multimedia contents

International audienceThe impact of confidentiality and privacy breaches are more pronounced when dealing with multimedia contents. One of the obvious techniques to counter these threats is the use of encryption. A number of algorithms for robust image encryption, targeted for real-time applications with tight resource constraints, has been proposed in the literature. In this paper, first, we analyze two recent cipher schemes for image contents, which are based on two rounds. We show that the schemes are designed to ensure maximum avalanche effect in the whole image by employing the chaining block code mode (CBC) in forward and backward directions. However, they do not lend themselves to parallel implementation and they have a problem with error propagation, which is not desirable for wireless multimedia transmission. As such, we propose to redesign the underlying algorithm to make it practical when used with applications that either suffer from a high error percentage or from real-time constraints. The modified cipher employs the counter mode to eliminate the chaining process (forward and backward), which allows for parallel computations and minimizes the effect of error propagation. According to the security and performance results, the proposed scheme can respond better to the applications and/or system requirements and limitations by ensuring a better performance and an equally high level of security compared to both ciphers in addition to minimum error propagation. To the best of our knowledge, the proposed scheme is the first dynamic key-dependent stream cipher scheme with a pseudo-random key-stream generation for re-ordering of sub-matrices