Biometric based authentication can provide strong security guarantee about the identity of users. Security of biometric data is particularly important as compromise of the data will be permanent. Cancelable biometrics store a non-invertible transformed version of the biometric data and so if the storage is compromised the biometric data remains safe. Cancelable biometrics also provide a higher level of privacy by allowing many templates for the same biometric data and hence nonlinkability of user's data stored in different databases. We define how to measure the success of a particular transformation and matching algorithm for fingerprints. We consider a key-dependent geometric transform that is applied to the features extracted from a fingerprint, to generate a key-dependent cancelable template for the fingerprint. We investigate performance of an authentication system that uses this cancelable fingerprint when a fingerprint matching algorithm is used for detection. We evaluate performance of the system and show the challenges of achieving good performance if the matching algorithm is not modified.

Intensity-modulated radiation therapy (IMRT) requires the determination of the appropriate multileaf collimator settings to deliver an intensity map. The purpose of this work was to attempt to reduce the number of segments required for IMRT delivery and the number of monitor units required to deliver an intensity map. An intensity map may be written as a matrix. Leaf sequencing was formulated as a problem of decomposing the matrix into a series of sub-matrices. Sets of random intensity matrices were created and the segmentations produced by applying different algorithms were compared. The number of segments, important if verification and record (VR) overhead is significant, and beam on times were examined. It is shown that reducing the value of the matrix entries by the maximum amount at each stage results in the smallest number of steps. Reducing the 2-norm (sum of the squares) of the matrix entries by the maximum amount at each step results in the smallest beam on time. Three new algorithms are introduced, two of which produce results that are superior to those generated by the algorithms of other researchers. The resulting methods can be expanded upon to include tongue and groove effects and leaf inter-digitization. With square random matrices of the order 15, the reduction in beam time and segmentation is up to 30-40%. Compared to previous algorithms, those presented here have demonstrated a reduction in the beam on time required to deliver an intensity map by 30-40%. Similarly, the number of segments needed to deliver an intensity map is also reduced.

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Abstract. Strong notions of security for unconditionally secure digital signature schemes (USDS) were recently proposed where security is defined based on notions of security in computationally-secure digital signatures. The traditional area of unconditionally secure authentication, however, is that of "authentication codes" (A-codes). Relations between primitives is central to cryptographic research. To this end, we develop a novel "general group-based A-code" framework which includes known types of group A-codes and their extensions, including the newly proposed USDS, and also allows other models to be systematically described and analysed. In particular, information theoretic analysis of these codes can be applied to USDS, establishing fundamental bounds on USDS parameters. A second contribution herein is a modular algebraic method of synthesising group codes from simpler A-codes, such that security of the group code follows directly from the component codes. We demonstrate our approach by constructing and analysing a USDS satisfying the 'strongest security notion'.

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