07-Biometrics-Lecture-7-Part2-2-2008-11-03

07-Biometrics-Lecture-7-Part2-2-2008-11-03 - Master SC...

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1 Biometrics http://scgwww.epfl.ch/courses Master SC – Information and Communication Security Dr. Andrzej Drygajlo Speech Processing and Biometrics Group Signal Processing Institute Ecole Polytechnique Fédérale de Lausanne (EPFL) Center for Interdisciplinary Studies in Information Security (ISIS)
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2 Iris Recognition Generalities Iridology Properties of the iris Applications Iris sensing Iris features (IrisCode) Iris matching Performance evaluation Identification
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3 Comparison Different eyes’ IrisCodes are compared by vector Exclusive-OR’ing them in order to detect the fraction of their bits that disagree.
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4 Hamming Distance Using a Boolean XOR similarity metric on the phasor bit strings generates similarity scores among different IrisCodes that are binomially-distributed and that therefore have tails that attenuate extremely rapidly The XOR operator detects disagreement between any corresponding pair of bits, while the AND operator ensures that the compared bits are both deemed to have been uncorrupted by eyelashes, eyelids, specular reflections, or other noise. 0 would represent a perfect match The norms (|| ||) of the resultant XOR'ed phase bit vectors and of the AND'ed mask vectors are then measured in order to compute a fractional Hamming Distance (HD) as the measure of the dissimilarity between any two irises, whose two phase code bit vectors are denoted { codeA, codeB } and whose mask bit vectors are denoted { maskA, maskB }: (code A code B) mask A mask B Hamming Distance mask A mask B ∩∩ =
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5 Hamming Distance
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6 Hamming Distance The Boolean operators XOR and AND are applied in vector form to binary strings of length up to the word length of the CPU, as a single machine instruction. Thus for example on an ordinary 32-bit machine, any two integers between 0 and 4 billion can be XOR'ed in a single machine instruction to generate a third such integer, each of whose bits in a binary expansion is the XOR of the corresponding pair of bits
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This note was uploaded on 06/25/2009 for the course MATH MAT 400 taught by Professor Jamespotvein during the Fall '08 term at University of Toronto- Toronto.

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07-Biometrics-Lecture-7-Part2-2-2008-11-03 - Master SC...

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