A three-dimensional approach towards measuring sender anonymity

Thesis (M.S.)--Wichita State University, College of Engineering, Dept. of Electrical Engineering and Computer Science.Privacy plays an indispensable role over internet transactions. There are existing methods in place which enhance the level of privacy over WorldWide Web (WWW). Anonymity intends to hide the identity of the user during web transactions. Sender anonymity attempts to hide the identity of the sender of a message. Various anonymous systems exist today which provide different levels of anonymity to their users. Comparing various anonymous systems on the Web by quantifying the degree of anonymity provided by them is a daunting and challenging task. This thesis illustrates with examples that existing measures in literature are not sufficient to fully characterize the anonymity provided by a system and introduces a new isolation measure. The new isolation measure is proposed based on the existence of outliers in a distribution which is critical towards quantifying the anonymity provided by the system. The need for three distinct aspects of anonymity is justified, important from the perspectives of a user, a system designer and an attacker, leading to a three-dimensional approach towards measuring sender anonymity. A 3-tuple metric is proposed, and various properties of metric are also discussed. The interpretation of proposed metric depends on the desired characteristics of the system. Two anonymous systems can be compared in terms of the degree of anonymity provided, using the proposed 3-tuple metric and appropriate weights reflecting the attributes desired in the system. The proposed metric is applied to quantify the degree of anonymity provided by various existing anonymous systems