Selective encryption provides the ability to strike a balance between security and processing demands, e.g., in mobile clients. Image encoding using wavelets, and especially wavelet packets, can be used for efficient selective encryption. We will show how two such methods work and discuss their advantages and disadvantages in terms of security and speed.

We discuss computationally e cient techniques for conÿdential storage and transmission of medical image data. Two types of partial encryption techniques based on AES are proposed. The ÿrst encrypts a subset of bitplanes of plain image data whereas the second encrypts parts of the JPEG2000 bitstream. We ÿnd that encrypting between 20% and 50% of the visual data is su cient to provide high conÿdentiality. ?

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A lightweight encryption scheme for visual data based on wavelet filter parametrization is discussed. Being a special variant of header encryption, the technique has an extremely low computational demand. Security assessement of low-dimensional parametrizations schemes show severe weaknesses. We show that using high-dimensional parametrizations the scheme may be employed in applications requiring a medium security level.