The Taub Faculty of Computer Science Events and Talks

Online infrastructure often depends on security-critical authorities such as logging, time, and certificate services. Authorities, however, are vulnerable to the compromise of one or a few centralized hosts yielding "weakest-link" security. We propose collective authorities or cothorities, an architecture enabling thousands of participants to witness, validate, and co-sign an authority's public actions, with moderate delays and costs. Hosts comprising a cothority form an efficient communication tree, in which each host validates log entries proposed by the root, and contributes to collective log-entry signatures. These collective signatures are small and efficient to verify, while embodying "strongest-link" trust aggregated over the collective. We present and evaluate a prototype cothority implementation supporting logging, time stamping, and public randomness (lottery) functions. We find that cothorities can scale to support over 4000 widely-distributed participants while keeping collective signing latencies to within a few seconds.

Bio:
Bryan Ford currently leads the Decentralized/Distributed Systems (DeDiS) research group at Yale University, but will be moving to EPFL in Lausanne, Switzerland in July 2015. Ford's work focuses broadly on building secure systems, touching on many particular topics including secure and certified OS kernels, parallel and distributed computing, privacy-preserving technologies, and Internet architecture. He has received the Jay Lepreau Best Paper Award at OSDI, and multiple grants from NSF, DARPA, and ONR, including the NSF CAREER award. His pedagogical achievements include PIOS, the first OS course framework leading students through development of a working, native multiprocessor OS kernel. Prof. Ford earned his B.S. at the University of Utah and his Ph.D. at MIT, while researching topics including mobile device naming and routing, virtualization, microkernel architectures, and touching on programming languages and formal methods.