Gérard D. Cohen

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of P is smaller than the original value, a contradiction. Hence g > 0 implies (3.4). If g = 1, then a final application of Lemma 3 shows that there is another solution to P = Pmin with g = 0. It suffices, therefore, to obtain the solutions to P = Pmin with g = 0. By Lemma 4, c a = 0 or 1. This together with (2.1), (2.6), and (3.4) readily yields the values(More)
Fuzzy commitment schemes, introduced as a link between biometrics and cryptography, are a way to handle biometric data matching as an error-correction issue. We focus here on finding the best error-correcting code with respect to a given database of biometric data. We propose a method that models discrepancies between biometric measurements as an erasure(More)
All known results on covering radius are presented, as well as some new results. There are a number of upper and lower bounds, including asymptotic results, a few exact determinations of covering radius, some extensive relations with other aspects of coding theory through the Reed-Muller codes, and new results on the least covering radius of any linear [II,(More)
Fuzzy sketches, introduced as a link between biometry and cryptography, are a way of handling biometric data matching as an error correction issue. We focus here on iris biometrics and look for the best error-correcting code in that respect. We show that two-dimensional iterative min-sum decoding leads to results near the theoretical limits. In particular,(More)
Let C be a code of length n over an alphabet of q letters. An n-word y is called a descendant of a set of t codewords x1, . . . , xt if yi ∈ {xi , . . . , xi} for all i = 1, . . . , n. A code is said to have the t-identifying parent property if for any n-word that is a descendant of at most t parents it is possible to identify at least one of them. We prove(More)
Given a subsetX of vertices in the n-cube, i.e. the n-dimensional Hamming space, we are interested in the solution for the traveling salesman problem, namely the minimal length of a cycle passing through all vertices of X . For a given number M , we estimate the maximum of these lengths when X ranges over all possible choices of sets ofM vertices.(More)
  • G Cohen
  • Social science & medicine
  • 1996
A picture of patients' satisfaction with interpersonal aspects of hospital-based care (including out-patient and accident and emergency services) was obtained from a postal survey of the general population of Lothian Region in south-east Scotland. Results were broadly in agreement with other national surveys and emphasized the high importance patients(More)
A number of upper and lower bounds are obtained for K( n, R), the minimal number of codewords in any binary code of length n and covering radius R. Several new constructions are used to derive the upper bounds, including an amalgamated direct sum construction for nonlinear codes. This construction works best when applied to normal codes, and we give some(More)