Jefferson's Wheel

Modern web applications make frequent use of third-party scripts, often in ways that allow scripts loaded from external servers to make unrestricted changes to the embedding page and access critical resources including private user information. Our paper describing tools to assist site administrators in understanding, monitoring, and restricting the behavior of third-party scripts embedded in their site, and what we’ve learned by using them, is now available: Yuchen Zhou and David Evans, Understanding and Monitoring Embedded Web Scripts, IEEE Symposium on Security and Privacy 2015.

Yuchen will present the paper at the Oakland conference (in San Jose) this May.

Project Site: ScriptInspector.org

Congratulations to Samee Zahur for winning the iDash Secure Genomics competition (Hamming Distance challenge task), sponsored by Human Longevity, Inc. A video of the event is available at http://www.humangenomeprivacy.org/.

Samee’s solution was built using Obliv-C, and the code will be posted soon.

I gave a keynote talk at the Applied Multi-Party Computation workshop at Microsoft Research Redmond on Multi-Party Computation in 2029: Boom, Bust, or Bonanza?. Despite the risk of being proved horribly wrong in 15 years, my slides are here (also available as [PPTX] and as a video):

There are well-written summaries of the talk by Mahnush Movahedi and Mahdi Zamani and the Aarhus Crypto Group.

Security exploits nearly always stem from attackers finding ways to violate assumptions system implementers relied upon. As a simple example, consider a classic buffer overflow attack which is possible because the implementers assumed (perhaps implicitly) that the size of some data could not exceed the buffer size, but an attacker found a way to create an input that violates that assumption.

In this work, joint with colleagues at Microsoft Research, we consider the implicit assumptions upon which secure use of single sign-on SDKs depends. Our study of three important authentication and authorization SDKs (including Facebook’s) supports the need for systematically explicating SDKs to uncover these assumptions. We found assumptions that were critical to secure use of the SDKs, but that were not clearly documented and were subtle enough to be missed by the majority of tested apps.

We advocate that a systematic explication process for uncovering these assumptions should be part of the engineering process for developing security-critical SDKs.

For details, see our paper:

Our paper on symmetric cut-and-choose is now available. The paper will be presented at CRYPTO 2013 in August.

Abstract. Beginning with the work of Lindell and Pinkas, researchers have proposed several protocols for secure two-party computation based on the cut-and-choose paradigm. In existing instantiations of this paradigm, one party generates k garbled circuits; some fraction of those are “checked” by the other party, and the remaining fraction are evaluated. We introduce here the idea of symmetric cut-and-choose protocols, in which both parties generate k circuits to be checked by the other party. The main advantage of our technique is that k can be reduced by a factor of 3 while attaining the same statistical security level as in prior work. Since the number of garbled circuits dominates the costs of the protocol, especially as larger circuits are evaluated, our protocol is expected to run up to 3 times faster than existing schemes. Preliminary experiments validate this claim.

Full paper (16 pages): [PDF]

Fraudulent mobile applications could trick users into entering sensitive passwords, and then send those passwords to rogue site operators. With current technologies, users have no way of knowing that when they enter a password it is going to the intended application. What is needed is a trusted path for password entry, so when users enter a password they can trust that it will only be visible to the trusted provider.

This paper presents a solution that does not require any modifications to existing apps or application servers, but modifies the Android kernel to establish a shared secret between the user and kernel as part of the boot process, and then uses that shared secret to provide a trusted path for password entry.

Tianhao Tong will present the paper at Moble Security Technologies (MoST) in San Francisco, CA, 23 May 2013.

Paper: Tianhao Tong and David Evans. GuarDroid: A Trusted Path for Password Entry. In Moble Security Technologies (MoST), San Francisco, CA, 23 May 2013. [PDF, 10 pages]

Code: GuarDroid.net

Samee Zahur and I have written a paper on Circuit Structures for Improving Efficiency of Security and Privacy Tools. The paper explores ways to design static circuits (as used in garbled circuit protocols and symbolic execution, among other things) to provide reasonable efficiency for algorithms that use common data structures like arrays. By taking advantage of somewhat predictable access patterns, as well as batching, our circuit structures are able to provide operations with amortized cost that is polylogarithmic in the size of the data structure (in contrast to naive approaches that would require effectively copying the entire data structure for each operation). Samee will present the paper at the IEEE Symposium on Security and Privacy (“Oakland”) in San Francisco in May.

Full paper (15 pages): [PDF]
Project: MightBeEvil.com/netlist

Code: http://github.com/samee/netlist

Our paper on strengthening secure computation protocols to resist stronger adversaries is now available:

Yan Huang, Jonathan Katz, and David Evans. Quid Pro Quo-tocols: Strengthening Semi-Honest Protocols with Dual Execution. In 33rd IEEE Symposium on Security and Privacy (“Oakland” 2012), San Francisco, CA. 20-23 May 2012. [PDF, 13 pages]

Yan Huang will present the paper at the Oakland conference (which will be held in San Francisco for the first time, after being in Berkeley/Oakland for the first 32 years!) in May.

Abstract: Known protocols for secure two-party computation that are designed to provide full security against malicious behavior are significantly less efficient than protocols intended only to thwart semi-honest adversaries. We present a concrete design and implementation of protocols achieving security guarantees that are much stronger than are possible with semi-honest protocols, at minimal extra cost. Specifically, we consider protocols in which a malicious adversary may learn a single (arbitrary) bit of additional information about the honest party’s input. Correctness of the honest party’s output is still guaranteed. Adapting prior work of Mohassel and Franklin, the basic idea in our protocols is to conduct two separate runs of a (specific) semi-honest, garbled-circuit protocol, with the parties swapping roles, followed by an inexpensive secure equality test. We provide a rigorous definition and prove that this protocol leaks no more than one additional bit against a malicious adversary. In addition, we propose some enhancements to reduce the overall information a cheating adversary learns. Our experiments show that protocols meeting this security level can be implemented at cost very close to that of protocols that only achieve semi-honest security. Our results indicate that this model enables the large-scale, practical applications possible within the semi-honest security model, while providing dramatically stronger security guarantees.

Full paper (13 pages): [PDF]
Project site: MightBeEvil.com

Austin DeVinney, who worked with us on GuardRails last summer and presented a poster at USENIX Security Symposium, was featured in Radford’s College of Science and Technology newsletter.

Information technology student Austin DeVinney’s interest and curiosity has paid off with a summer internship opportunity with cybersecurity expert and Associate Professor of Computer Science at the University of Virginia David Evans.

The full article is here:
IT Student Presents Research at Prestigious Conference [PDF].

I gave a keynote talk on our secure computation work at the Seventh International Conference on Information Systems Security (ICISS) in Jadavpur University, Kolkata, India. 17 December 2011.

More Photos

Talk Slides: [PPTX] [PDF]