Nicholas J. Hopper Assistant Professor Computer Science & Engineering Department University of Minnesota hopper at cs umn edu Office: EECS 4-211 (612)-626-1284

Research

• What should it mean for a computer system to be secure? In order to prove the security of a system or protocol we must first establish formal definitions of security. 
  
  
• What can we prove about the security of current systems and protocols? Given a formal security goal, it is sometimes possible to prove that existing protocols satisfy this definition or show that they do not.
  
  
• How can we construct efficient systems with provable security properties? If we cannot prove the security of an existing protocol or system, a natural alternative is to construct a system so that the proof of security is tractable.  

Papers

In submission

Peer-reviewed Conference/Workshops

Jon McLachlan and Nicholas Hopper. "Don't Clog the Queue: Circuit Clogging and Mitigation in P2P anonymity schemes," at Financial Crypto 2008.

Nicholas Hopper, Eugene Y. Vasserman, and Eric Chan-Tin. "How much anonymity does network latency leak?" at CCS 2007.

Eugene Vasserman, Nicholas Hopper, John Laxson, and James Tyra.  "SilentKnock: Practical and Provably Undetectable Authentication." at ESORICS 2007.

Ivan Osipkov, Eugene Vasserman, Nicholas Hopper and Yongdae Kim. "Combatting Double-Spending Using Cooperative P2P Systems." at ICDCS 2007.

Nicholas Hopper, David Molnar, and David Wagner.  "From Weak to Strong Watermarking." at 4th Theoretical Cryptography Conference: TCC 2007.  (Full version)

Nicholas Hopper and Eugene Vasserman. "On the effectiveness of k-anonymity against traffic analysis and surveillance," at Privacy in the Electronic Society: WPES 2006.

Luis von Ahn, Andrew Bortz, Nicholas Hopper, and Kevin O'Neill.  "Selectively Traceable Anonymity," at Privacy Enhancing Technologies: PET 2006.

Ivan Osipkov, Peng Wang, Nicholas Hopper and Yongdae Kim.  "Robust Accounting in Decentralized P2P Storage Systems," at ICDCS 2006.

Jung Hee Cheon, Nicholas Hopper, Yongdae Kim and Ivan Osipkov.  "Authenticated Key-Insulated Public Key Encryption and Timed-Release Cryptography," at Financial Crypto 2006.

Nicholas Hopper. "On Steganographic Chosen Covertext Security," at ICALP 2005.

Luis von Ahn, Nicholas J. Hopper, and John Langford. "Covert Two-Party Computation," at STOC 2005.

Luis von Ahn and Nicholas J. Hopper. " Public-Key Steganography," at Eurocrypt 2004.

Luis von Ahn, Andrew Bortz, and Nicholas J. Hopper. "k-Anonymous Message Transmission," at CCS 2003.

Luis von Ahn, Manuel Blum, Nicholas J. Hopper and John Langford. " CAPTCHA: Using Hard AI Problems for Security," at Eurocrypt 2003.

Nicholas J. Hopper, John Langford, and Luis Von Ahn. " Provably Secure Steganography," at Crypto 2002.

Nicholas J. Hopper and Manuel Blum. " Secure Human Identification Protocols," at Asiacrypt 2001.

Nicholas J. Hopper, Sanjit A. Seshia, and Jeanette M. Wing, "Combining Theory Generation and Model Checking for Security Protocol Analysis," at Formal Methods in Computer Security, July 2000. Also available as CMU Technical Report CMU-CS-00-107, January 2000.

Nicholas Freitag McPhee and Nicholas J. Hopper. " Analysis of Genetic Diversity through Population History," in GECCO99: Proceedings of the Genetic and Evolutionary Computation Conference, July 1999.

Nicholas Freitag McPhee and Nicholas J. Hopper. " AppGP: An alternative structural representation for GP," in Proceedings of the 1999 Congress on Evolutionary Computation, June 1999.

Nicholas Freitag McPhee, Nicholas J. Hopper, and Mitchell L. Reierson. " Impact of types on essentially typeless problems in GP," in Genetic Programming 1998: Proceedings of the Third Annual Conference, July 1998.

Other

Nicholas J. Hopper. "Toward a Theory of Steganography," CMU Ph.D. Thesis, 2004.

Nicholas J. Hopper and Manuel Blum, "A Secure Human-Computer Authentication Scheme", CMU Technical Report CMU-CS-00-139, May 2000.

Teaching

Etc.