Robert Eliot Shostak (born July 26, 1948, in Arlington, Virginia) is an American computer scientist and Silicon Valley entrepreneur. He is most noted academically for his seminal work in the branch of distributed computing known as Byzantine Fault Tolerance. He is also known for co-authoring the Paradox Database, and most recently, the founding of Vocera Communications, a company that makes wearable, Star Trek-like communication badges.
Shostak has authored more than forty academic papers and patents, and was editor of the 7th Conference on Automated Deduction. He has Erdős number 2 through his collaboration with Kenneth Kunen.
Shostak is a brother of Seth Shostak, who is Senior Astronomer at the SETI Institute and who frequently appears on television and radio.
Education
Robert Shostak was born in a Jewish family in Arlington, Virginia, the son of Arthur and Bertha Shostak (née Gortenburg); his father was an electrical engineer. He studied mathematics and computer science at Harvard College, graduating in 1970 with high honors. As part of his senior dissertation work, he designed and built one of the earliest personal computers using discrete RTL logic (microprocessors were not yet available) and a magnetic core memory. He continued at Harvard to earn his A.M. degree and Ph.D. in Computer Science in 1974. While at Harvard he was awarded the Detur Book Priz', and fellowships from IBM and the National Science Foundation.
Career
Afterwards, Shostak joined the research staff in the Computer Science Lab (CSL) at SRI International (formerly the Stanford Research Institute) in Menlo Park, California. Much of his work there focused on automated theorem proving, and specifically on the development of decision procedure algorithms for mechanized proof of the kinds of mathematical formulas that occur frequently in the formal verification of correctness of computer programs.
In collaboration with CSL's Richard L. Schwartz and P. Michael Melliar-Smith, Shostak implemented a semi-automatic theorem prover incorporating some of these decision procedures. The prover was used to verify correctness properties of an abstract specification of the SIFT (for Software Implemented Fault Tolerance) operating system and was later incorporated into SRIís Prototype Verification System. The work was published in the paper, SIFT: Design and analysis of a fault-tolerant computer for aircraft control This paper was awarded the 2014 Jean-Claude Laprie Award in Dependable Computing established by the IFIP Subgroup 10.4 on Dependable Computing.
Interactive Consistency and Byzantine Fault Tolerance
Perhaps Shostak's most notable academic contribution is to have originated the branch of distributed computing known as Byzantine fault tolerance, also called interactive consistency.
This work was also conducted in connection with the SIFT project at SRI. SIFT was conceived by John H. Wensley, who proposed using a network of general-purpose computers to reliably control an aircraft even if some of those computers were faulty. The computers would exchange messages as to the current time and state of the aircraft (each would have its own sensors and clock), and would thereby reach a consensus.
At the outset, it was unknown how many computers would be necessary to reach consensus if some n of them were faulty, and possibly acting in a 'malicious' manner to thwart consensus. Shostak formalized the problem mathematically and proved that for n faulty computers, no fewer than 3n+1 computers in total were needed for any algorithm that could guarantee consensus, or what he termed interactive consistency. He also devised an algorithm for n = 1, proving that four computers were sufficient using two rounds of message passing. His colleague Marshall Pease then generalized the result by constructing an algorithm for 3n+1 computers that works for all n > 0, thus showing that 3n+1 are sufficient as well as necessary.
Leslie Lamport later joined the CSL, and showed that if messages could be digitally signed, then only 3n are needed.
The collective results were published in 1979 in the seminal paper, Reaching Agreement in the Presence of Faults, which was awarded the 2005 Edsger W. Dijkstra Prize in Distributed Computing, as well as the 2013 Jean-Claude Laprie Award