JPEG XR is the most recent still image coding standard, and custom security features for this format are required for fast adoption of the standard. Format-compliant encryption schemes are important for many application scenarios but need to be highly customised to a specific recent format like JPEG XR. This paper proposes, discusses, and evaluates a set of format-compliant encryption methods for the JPEG XR standard: coefficient scan order permutation, sign bit encryption, transform-based encryption, random level shift encryption, index-based VLC encryption, and encrypting entire frequency bands are considered. All algorithms are thoroughly evaluated by discussing possible compression impact, by assessing visual security and cryptographic security, and by discussing applicability in real-world scenarios. Most techniques are found to be insecure and, in a cryptographic sense, have a limited range of applicability and cannot be applied to JPEG XR bitstreams in an efficient manner. Encrypting entire frequency bands is identified to be a good solution in case a weaker form of format compliance can be accepted.
The impact of using different lossy compression algorithms on the recognition accuracy of iris recognition systems is investigated. In particular, we consider the general purpose still image compression algorithms JPEG, JPEG2000, SPIHT, and PRVQ and assess their impact on ROC of two different iris recognition systems when applying compression to iris sample data.
The paper presents a metric for visual security evaluation of encrypted images based on object recognition using the Scale Invariant Feature Transform (SIFT). The metrics' behavior is demonstrated using three different encryption methods and its performance is compared to that of the PSNR, SSIM and Local Feature Based Visual Security Metric (LFBVSM). Superior correspondance to human perception and better responsiveness to subtle changes in visual security are observed for the new metric.
We present a wizard of Oz framework for the simulation of locationbased mobile games. We explore briefly the methodological concept of Wizard of Oz and show, based on a case study, advantages and shortcomings of the method. The case study realized a game called capture-the-flag. We show how such prototypes can be evaluated in a real field trial.
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