An Algebraic Approach for Reasoning About Information Flow

Abstract

This paper concerns the analysis of information leaks in security systems. We address the problem of specifying and analyzing large systems in the (standard) channel model used in quantitative information flow (QIF). We propose several operators which match typical interactions between system components. We explore their algebraic properties with respect to the security-preserving refinement relation defined by Alvim et al. and McIver et al. [1,2]. We show how the algebra can be used to simplify large system specifications in order to facilitate the computation of information leakage bounds. We demonstrate our results on the specification and analysis of the Crowds Protocol. Finally, we use the algebra to justify a new algorithm to compute leakage bounds for this protocol. arXiv:1801.08090v4 [cs.CR] 8 Jul 2018Crypto 1 (t 1 , t 2 , t 3 , t 4 , x) = 1, if t 4 = t 1 and x = c 1 , or t 4 = t 1 and x = c 1 0, otherwise Channels Crypto 2 , Crypto 3 and Crypto 4 describing the remaining cryptographers are defined analogously. Channel Announcements is, hence, defined as Announcements = Crypto 1 Crypto 2 Crypto 3 Crypto 4 .Proposition 7. Let D 1 : Y 1 ×Z 1 → R, D 2 : Y 2 ×Z 2 → R be channels. Then,

Defining and Controlling Information Leakage in US Equities Trading

“…As a result, much effort in the field has been dedicated to defining ways of composing channels, and studying their properties [6,Chapter 8]. These compositionality results have been useful in studying the leakage of information in anonymity protocols [8,25,34], timing attacks against cryptosystems [38], two-player games [5], and in scenarios where the sensitive data that is correlated to the input [14]. We adopt this compositional approach in our work, using the parallel and cascading compositions [6,Chapter 8] to obtain, from simpler and more intuitive channels, a comprehensive model of the effect a trader Alice's actions have in the market.…”

“…, 1). Notice that all operations above, and the cascading and parallel operations in (8), are linear operations w.r.t. the entries of 𝐴𝑙𝑖𝑐𝑒 Similarly, letting 𝐴 be the r.v.…”

Fairness analysis of extra-gain guilty of a non-repudiation protocol

“…Fairness Fairness is a very important factor because it has nothing to do with network size or complexity. The goal of fairness is to guarantee that benefits are distributed fairly among the participants in an activity (Zhao et al, 2016;Américo et al, 2018;Said and Cristescu, 2020). Informally, fairness means that at each step of the protocol, either both parties receive their expected items, or neither of them receives any valuable information about their expected items.…”