N. Hopper

Publications
Influence

CAPTCHA: Using Hard AI Problems for Security

L. V. Ahn, M. Blum, N. Hopper, J. Langford
Computer Science
EUROCRYPT
4 May 2003

We introduce captcha, an automated test that humans can pass, but current computer programs can't pass: any program that has high success over a captcha can be used to solve an unsolved Artificial Intelligence (AI) problem. Expand

1,443
124
PDF

Secure Human Identification Protocols

N. Hopper, M. Blum
Computer Science
ASIACRYPT
9 December 2001

In this paper, we provide definitions of what we believe to be reasonable goals for secure human identification. Expand

Shadow: Running Tor in a Box for Accurate and Efficient Experimentation

Rob Jansen, N. Hopper
Computer Science
NDSS
23 September 2011

We present the design and implementation of Shadow, an architecture for efficiently running accurate Tor experiments on a single machine. Expand

Analysis of genetic diversity through population history

N. McPhee, N. Hopper
Biology
13 July 1999

The idea that diversity in the population of a genetic algorithm affects the algorithm's search efficiency is widely accepted. Expand

How much anonymity does network latency leak?

N. Hopper, E. Vasserman, Eric Chan-Tin
Computer Science
ACM Trans. Inf. Syst. Secur.
1 February 2010

We present two attacks on low-latency anonymity schemes using this information. Expand

k-anonymous message transmission

L. V. Ahn, A. Bortz, N. Hopper
Computer Science
CCS '03
27 October 2003

We show that there exist simple protocols which are k-anonymous for both the sender and the receiver in a model where a polynomial time adversary can see all traffic in the network and can control up to a constant fraction of the participants. Expand

Scalable onion routing with torsk

Jon McLachlan, Andrew Tran, N. Hopper, Y. Kim
Computer Science
CCS
9 November 2009

We introduce Torsk, a structured peer-to-peer low-latency anonymity protocol that decreases the bandwidth cost of relay selection and maintenance from quadratic to quasilinear while introducing no new attacks on the anonymity provided by Tor, and no additional delay to connections made via Tor. Expand

Routing around decoys

Max Schuchard, J. Geddes, C. Thompson, N. Hopper
Computer Science
CCS
16 October 2012

We show that a routing capable adversary can enumerate the participating routers implementing these protocols; can successfully avoid sending traffic along routes containing these routers with little or no adverse effects. Expand

Vampire Attacks: Draining Life from Wireless Ad Hoc Sensor Networks

E. Vasserman, N. Hopper
Computer Science
IEEE Transactions on Mobile Computing
1 February 2013

This paper explores resource depletion attacks at the routing protocol layer, which permanently disable networks by quickly draining nodes' battery power. Expand

Keep your friends close: Incorporating trust into social network-based Sybil defenses

Aziz Mohaisen, N. Hopper, Y. Kim
Computer Science
Proceedings IEEE INFOCOM
1 April 2011

In this paper we introduce several designs to tune the performance of Sybil defenses by accounting for differential trust in social graphs and modeling these trust values by biasing random walks performed on these graphs. Expand

Recommended Authors