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Information content of biometric features Andy Adler, Richard Youmaran, Sergey Loyka

Summary: Information content of biometric features
Andy Adler, Richard Youmaran, Sergey Loyka
University of Ottawa, Ontario, Canada
1. Introduction
How much information is there in a face, or a fingerprint? In this paper we elaborate an approach to address this question
based on information theory reasoning. In order to motivate our approach, we initially consider the properties that such a
measure should have. Consider a soft biometric system which measures height and weight; furthermore, assume all humans
are uniformly and independently distributed in height between 100200 cm and weight between 100200 lb. If a person's
features were completely stable and could be measured with infinite accuracy, people could be uniquely identified from these
measurements, and the biometric features could be considered to yield infinite information. However, in reality, repeated
biometric measurements give different results due to measurement inaccuracies, and to short- and long-term changes in the
biometric features themselves. If this variability results in an uncertainty of 5 cm and 5 lb, one simple model would be to
round each measure measure to 105, 115, ..., 195. In this case, there are 10 10 equiprobable outcomes, and an information
content of log2(100) = 6.6 bits.
Such an analysis is intrinsically tied to a choice of biometric features. Thus, it does not appear possible to answer "how
much information is in a fingerprint?", but only "how much information is in the position and angle data of fingerprint
minutiae?". Furthermore, for many biometrics, it is not clear what the underlying features are. Face images, for example,
can be described by image basis features or landmark based features. To overcome this, we may choose to calculate the
information in all possible features. In the example, we may provide height in inches as well as cm; however, in this case, a


Source: Adler, Andy - Department of Systems and Computer Engineering, Carleton University


Collections: Computer Technologies and Information Sciences