An evaluation of lightweight JPEG2000 encryption with anisotropic wavelet packets

In this paper we evaluate a lightweight encryption scheme for JPEG2000 which relies on a secret transform domain constructed with anisotropic wavelet packets. The pseudo-random selection of the bases used for transformation takes compression performance into account, and discards a number of possible bases which lead to poor compression performance. Our main focus in this paper is to answer the important question of how many bases remain to construct the keyspace. In order to determine the trade-off between compression performance and keyspace size, we compare the approach to a method that selects bases from the whole set of anisotropic wavelet packet bases following a pseudo-random uniform distribution. The compression performance of both approaches is compared to get an estimate of the range of compression quality in the set of all bases. We then analytically investigate the number of bases that are discarded for the sake of retaining compression performance in the compression-oriented approach as compared to selection by uniform distribution. Finally, the question of keyspace quality is addressed, i.e. how much similarity between the basis used for analysis and the basis used for synthesis is tolerable from a security point of view and how this affects the lightweight encryption scheme.