BIB-VERSION:: CS-TR-v2.0 ID:: ncstrl.dartmouthcs//TR2008-637 ENTRY:: December 07, 2008 ORGANIZATION:: Dartmouth College, Computer Science REQUESTED-BY:: sws@cs.dartmouth.edu REQUESTED-FOR:: patrick@cs.dartmouth.edu REQUESTED-DATE:: Sun Nov 30 20:56:46 EST 2008 TITLE:: Nymble: Blocking Misbehaving Users in Anonymizing Networks TYPE:: Technical Report (paper) REVISION:: 1 AUTHOR:: Tsang, Patrick P. AUTHOR:: Kapadia, Apu AUTHOR:: Cornelius, Cory AUTHOR:: Smith, Sean W. DATE:: December 2008 RETRIEVAL:: For a paper copy, email RETRIEVAL:: For a paper copy, write to Technical Report Librarian Department of Computer Science Dartmouth College 6211 Sudikoff Laboratory Hanover, NH 03755-3510 USA RETRIEVAL:: PDF at http://www.cs.dartmouth.edu/reports/TR2008-637.pdf ABSTRACT:: Anonymizing networks such as Tor allow users to access Internet services privately by using a series of routers to hide the client's IP address from the server. The success of such networks, however, has been limited by users employing this anonymity for abusive purposes such as defacing popular websites. Website administrators routinely rely on IP-address blocking for disabling access to misbehaving users, but blocking IP addresses is not practical if the abuser routes through an anonymizing network. As a result, administrators block \emph{all} known exit nodes of anonymizing networks, denying anonymous access to misbehaving and behaving users alike. To address this problem, we present Nymble, a system in which servers can ``blacklist'' misbehaving users, thereby \emph{blocking users without compromising their anonymity}. Our system is thus agnostic to different servers' definitions of misbehavior --- servers can blacklist users for whatever reason, and the privacy of blacklisted users is maintained. NOTE:: Nymble first appeared in a PET '07 paper. This paper presents a significantly improved construction and a complete rewrite and evaluation of our (open-source) implementation. END:: ncstrl.dartmouthcs//TR2008-637