Title:

OrgAn: Organizational Anonymity with Low Latency

 

Abstract:

There is a growing demand for network-level anonymity for delegates at global organizations such as the UN and Red Cross. Numerous anonymous communication (AC) systems have been proposed over the last few decades to provide anonymity over the internet; however, they introduce high latency overhead, provide weaker anonymity guarantees, or are difficult to deploy at the organizational networks. Recently, the PriFi system introduced a client/relay/server model that suitably utilizes the organizational network topology and proposes a low-latency, strong-anonymity AC protocol. Using an efficient lattice-based (almost) key-homomorphic pseudorandom function and Netwon's power sums, we present a novel AC protocol OrgAn in this client/relay/server model that provides strong anonymity against a global adversary controlling the majority of the network. OrgAn's cryptographic design allows it to overcome several major problems with any realistic PriFi instantiation:
(a) unlike PriFi, OrgAn avoids frequent, interactive, slot-agreement protocol among the servers;
(b) a PriFi relay has to receive frequent communication from the servers, which can not only become a latency bottleneck but also reveal the access pattern to the servers and increases the chance of server collusion/coercion, while OrgAn servers are absent from any real-time process. We demonstrate how to make this public-key cryptographic solution scale equally well as the symmetric-cryptographic PriFi with practical pre-computation and storage requirements. Through a prototype implementation, we show that OrgAn provides similar throughput and end-to-end latency guarantees as PriFi, while still discounting the setup challenges in PriFi.

 

Speaker:

Debajyoti Das

Postdoctoral Researcher
COSIC Privacy Group
KU leuven

 

Bio:

Debajyoti Das is a postdoctoral researcher in COSIC Privacy Group at KU Leuven. He received his Ph.D. from Purdue University under the supervision of Prof. Aniket Kate.
His research interests lie at the intersection of cryptography and privacy – mainly focusing on design, implementation and analysis of privacy-preserving systems. He worked on designing privacy-preserving protocols like cMix, OrgAn, Streams, and SortingHat. Currently he is working on building provably secure anonymous communication networks that can scale for a large number of users without introducing high latency overhead.