Speaker:
Stanislav Kruglik
NTU Singapore

Abstract:
Private Information Retrieval (PIR) is a cryptographic primitive that enables aclient to retrieve a record from a database hosted by one or more untrustedservers without revealing which record was accessed. It has a wide range ofapplications, including private web search, private DNS, lightweightcryptocurrency clients, and more. While many existing PIR protocols assume thatservers are honest but curious, we explore the scenario where dishonest serversprovide incorrect answers to mislead clients into retrieving the wrong results.

We begin by presenting a unified classification of protocols that addressincorrect server behavior, focusing on the lowest level ofresistance—verifiability—which allows the client to detect if the retrievedfile is incorrect. Despite this relaxed security notion, verifiability issufficient for several practical applications, such as private media browsing.

Later on, we propose a unified framework for polynomial PIR protocols,encompassing various existing protocols that optimize download rate or totalcommunication cost. We introduce a method to transform a polynomial PIR into averifiable one without increasing the number of servers. This is achieved bydoubling the queries and linking the responses using a secret parameter held bythe client.

About: Stanislav Kruglik has been a Research Fellow at the School ofPhysical and Mathematical Sciences, Nanyang Technological University,Singapore, since April 2022. He earned a Ph.D. in the theoretical foundationsof computer science from the Moscow Institute of Physics and Technology,Russia, in February 2022. He is an IEEE Senior Member and a recipient of theSimons Foundation Scholarship. With over 40 scientific publications, his workhas appeared in top-tier venues, including IEEE Transactions on InformationForensics and Security and the European Symposium on Research in ComputerSecurity. His research interests focus on information theory and itsapplications, particularly in data storage and security.

The weekly security seminar has been held every semester since spring of 1992. We invite personnel at Purdue and visitors from outside to present on topics of particular interest to them in the areas of computer and network security, computer crime investigation, information warfare, information ethics, public policy for computing and security, the computing "underground," and other related topics. More info