In the current internet landscape, cryptography plays a central role in securing communication. We rely on mathematical proofs to ensure security of the cryptographic systems that are deployed in practice. However, in many cases, due to issues like efficiency constraints, there is a gap between what these deployments need and what we can prove. In this talk, I will describe how my research identifies these gaps and makes progress towards bridging these gaps using new theoretical insights and techniques from different areas of computer science like complexity theory, algorithms, combinatorics, information theory, etc.
More concretely, my work contributes towards bridging these gaps in three different ways. First, I provide exact security analyses of cryptographic systems that have been deployed at scale that did not have such analyses before. With the exact analyses available, practitioners can set parameters of the cryptographic system in a way that maximizes efficiency without sacrificing security. Secondly, I construct new cryptographic schemes that are better than existing schemes in terms of efficiency. This work helps make purely theoretical cryptographic notions practical. Finally, my work incorporates newer perspectives into the framework of security proofs that captures a more complete picture of the real world. This is in contrast to prior work where only certain adversarial resources were taken into account. A more complete picture of adversarial resources often helps in setting parameters in a way that increases efficiency of cryptographic systems.

Short Bio: Ashrujit Ghoshal is a postdoctoral fellow at Carnegie Mellon University. He received his PhD from the University of Washington in 2023. His research focuses on bridging the gap between the theory and practice of cryptography by developing new theory that characterizes security and efficiency of cryptographic systems as precisely as possible. In particular his work has provided exact security analyses for cryptography that is widely used in practice e.g., standard hash functions like SHA-2 and SHA-3, TLS, etc. His work has also made progress towards making theoretical cryptographic functionalities like private information retrieval more practical by giving new concretely efficient constructions. These works have led to multiple papers at the two top cryptography conferences- CRYPTO and EUROCRYPT.