Title: When not all bits are equal: incorporating "worth" into  
information-flow measures

Authors: Mário S. Alvim, Andre Scedrov, Fred B. Schneider

Abstract: 

Approaches to quantitative information flow (QIF)  
traditionally have presumed that all leaks involving a given number of  
bits are equally harmful. The presumption is unrealistic, so in the  
FCS workshop we will discuss our approach to the problem. Secrets are  
defined in terms of fields, where derived secrets obtained by  
combining these fields can be assigned a different "worth" (perhaps in  
proportion to the harm that would result from disclosure). New  
measures that incorporate worth into QIF are then discussed; they  
generalize probability of guessing, guessing entropy, and Shannon  
entropy. A lattice of information is derived to provide an underlying  
algebraic structure for an adversary's state of knowledge in this  
more-general setting.