Application Aware Anonymity (A3)


Application-Aware Anonymity (A3) is an extensible platform for applications to deploy anonymity-based services on the Internet. A3 allows applications to tailor their anonymity properties and performance characteristics according to their specific communication requirements. For example, A3 permits an anonymous voice-over-IP application to produce anonymous paths with low latency and jitter, while providing anonymous file transfer applications with high bandwidth (but not necessarily low latency or jitter) routes.

To support flexible path construction, A3 exposes a declarative language (A3Log) that enables applications to compactly specify path selection and instantiation policies which are then executed using a declarative networking engine. We demonstrate that our declarative language is sufficiently versatile to represent novel multi-metric performance constraints as well as existing relay selection algorithms used by Tor and other anonymity systems, using only a few lines of concise code. In addition to specifying relay selection strategies, senders are able to use our declarative techniques to construct anonymous tunnels according to their specifications (for example, via Onion Routing or Crowds). We experimentally evaluate the A3 system using a combination of trace-driven simulations and deployment on PlanetLab. Our experimental results demonstrate that the A3 system can flexibly support a wide range of path selection and instantiation strategies at low performance overhead.



An experimental release of A3 is now available for download. Please note that this release is designed for research purposes, and should not be relied upon for strong anonymity.

A3 is released under the GPLv2 license.


Project Members

A3 is a collaborative effort between Georgetown University and the University of Pennsylvania.

Prof. Micah Sherr, Project Lead (Georgetown)
Prof. Matt Blaze, Project Lead (Penn)
Prof. Boon Thau Loo, Project Lead (Penn)
Harjot Gill (Penn)
Taher Saeed (Penn)
Bill Marczak (Formerly Penn, now at University of California at Berkeley)
Qiushi (Andrew) Mao (Formerly Penn, now at Harvard University)
Kefei (Dan) Zhou (Penn Alumnus)
Wenchao Zhou (Penn)
Sheng Quan Zhuang (Penn Alumnus)




Contact Info

For more information, please email Micah Sherr.



Please see the Veracity website for more information.



The A3 project is partially supported by NSF Grants CNS-0831376, CNS-0524047, CNS-0627579, and NeTS-0721845. Any opinions, findings, and conclusions or recommendations expressed in this material are those of the author(s) and do not necessarily reflect the views of the National Science Foundation.