CS 6113 Lecture 19 Quantitative Information Flow 12 November 2013

Quantitative information flow was first proposed by Denning [5] and Gray [6]. Its goal is to measure the amount of information leaked about a secret by observing the running of a program. Quantitative definitions of information leakage are often borrowed from information theory. Indeed, early models of quantitative information flow directly used the Shannon mutual information I(X;Y ), which measures the (expected) reduction in uncertainty about the value of random variable X given by learning the value of Y (see §2). Doing information flow quantitatively immediately raises the following issues, among others: