David Cash, a researcher specializing in theoretical and applied cryptography, joined the University of Chicago Computer Science Department as an Associate Professor in Winter 2018.
Cash’s work straddles cryptography and its applications in cybersecurity, covering topics such as public key encryption, post-quantum cryptography, and encrypted databases and search. He has also published papers on the basic theory of cryptography and taught classes on discrete math.
“Crypto is unique in that it's the only place where discrete math and number theory is applied in a way that matters in a very visceral sense to the world: stopping criminals from doing bad things,” Cash said. “More generally, my research analyzes the ways systems use crypto and the way information leaks out of them, depending on how the crypto is used.”
For example, Cash has recently focused on cybersecurity questions around how cloud-based services such as Gmail or Dropbox handle user information. Currently, these systems need to “see” a user’s emails or files to perform basic searches, and architectures that incorporate encryption present major technical and legal challenges.
“With these applications, security is in direct tension with what you want,” Cash said. “I’ve been working for the last several years on how can we design encryption through some very controlled release of information so services can selectively help you search the documents without just ripping them all open and taking a look for you. We’re designing the crypto in an intelligent way to enable that.”
While studying encrypted search and databases, Cash also stumbled upon a security flaw in the way some services, including Github, handle document retrieval. Cash and colleagues found that these systems were vulnerable to “side-channel attacks,” and developed countermeasures that they shared with susceptible services.
“That turned out to be a non-crypto project,” Cash said. “But the cryptographic perspective that I was coming from made the flaw easy to see at an abstract level.”
On the more theoretical side, Cash is interested in new cryptographic approaches in the context of streaming algorithms and quantum computation. Because quantum computers may soon be capable of solving the integer factorization that underlies the public key cryptography used by most of today’s internet, Cash creates and tests new encryption strategies that aim to remain secure.
Before coming to UChicago, Cash served as assistant professor at Rutgers University and performed postdoctoral research at the IBM T.J. Watson Research Center, Ruhr-University Bochum, and the University of California, San Diego.
“The university is such an amazing, interesting place,” Cash said.“The security group is a great fit for me, and I'm already finding the department a great place to collaborate on research... the intellectual community here got me really excited.”
University of Chicago