Newswise — UNIVERSITY PARK, Pa. – People that shop online often take for granted the cryptography that keeps their credit card information secure from third parties. But there’s no guarantee that retailers will always have the best cryptography in place to protect their customers once large-scale quantum computers are built. Currently used systems can be broken using such a computer.

Sean Hallgren, professor of computer science and engineering, Penn State, whose research focuses on quantum computation and theoretical computer science, has received an award from the Department of Defense (DoD) to work on quantum algorithms. One aspect of this is determining which encryption cannot be broken by quantum computers.

Hallgren is one of 11 distinguished faculty to be named to the 2018 Class of Vannevar Bush Faculty Fellows (VBFF) by the DoD. The program provides awards to top-tier engineers and scientists from U.S. universities to conduct “high-risk, high-payoff” research in areas of interest to the DoD over five years, with up to $3 million in support. 

According to the DoD, “VBFF is oriented towards bold and ambitious ‘blue sky’ research that may lead to extraordinary outcomes such as revolutionizing entire disciplines, creating entirely new fields, or disrupting accepted theories and perspectives.”

Hallgren will concentrate on the field of quantum algorithms, to determine how to keep cryptography secure. In his abstract, “Exponential Speedups and Limitations of Quantum Computation,” Hallgren explained that he’ll be looking at problems that quantum computers can solve but classical computers cannot solve efficiently, specifically in terms of cryptography. Hallgren hopes his work will help the DoD understand what quantum computers are capable of, as well as work on encryption security in the future.

“Currently used systems can be broken using large scale quantum computers. So far only small quantum computers are available, and cryptography must be replaced before large systems are built,” Hallgren said. “Some of the main proposals for new cryptosystems are lattice-based systems. It is unknown if a quantum computer can solve lattice problems, but if they can, then these systems would also be insecure. This goal of this research is about determining whether or not quantum computers can solve lattice problems.”

Hallgren explained that while this is a critically important question, it would not be funded by a regular research grant because the problem is too hard. 

“For one thing, if you spend time trying to find a quantum algorithm for these problems, but one does not exist, then you probably end up with no research results,” he said. “Second, even if there is an algorithm, there are no obvious measurable steps to take towards finding it. All the straightforward approaches have been tried. But the upside is that if we are successful in finding quantum algorithms for lattice problems, it will be a major breakthrough in our understanding of what quantum computers can solve, and it will also have a large impact on cryptography.”

Hallgren said it could take multiple years with very little to show, even if the final result is a major breakthrough. Part of the challenge with this area is its interdisciplinary nature. It requires expertise in quantum computation, number theory, theoretical computer science, and cryptography. The DoD fellowship gives him the unique opportunity to carry out this research: it has a longer time frame of five years, and also does not have milestones like a normal grant. It also provides a funding level to put all the pieces in place. 

Hallgren will also have help with the project. Kirsten Eisentraeger, professor in the Department of Mathematics, Penn State, will be a key part of his work as senior personnel. 

“Her number theory expertise will help with the deep mathematical questions that arise in some of the cryptography applications, and we will build on previous collaborations that we’ve had,” Hallgren said. “The group will also include a postdoctoral fellow and students.”

Hallgren joined Penn State in 2007 and received the Presidential Early Career Award for Scientists and Engineers (PECASE) in 2009.