Dr. Rohit Chatterjee, National University of Singapore gave an online talk on The Round Complexity of Black-Box Post-Quantum Secure Computation on 25 June. Here is the summary of the talk as explained by Dr. Rohit Chatterjee:
We close the gap between black-box and non-black-box constructions of composable secure multiparty computation in the plain model under the minimal assumption of semi-honest oblivious transfer. The notion of protocol composition we target is angel-based security, or more precisely, security with super-polynomial helpers. In this notion, both the simulator and the adversary are given access to an oracle called an angel that can perform some predefined super-polynomial time task. Angel-based security maintains the attractive properties of the universal composition framework while providing meaningful security guarantees in complex environments without having to trust anyone. Angel-based security can be achieved using non-black-box constructions in max(ROT, Oe(log n)) rounds where ROT is the round-complexity of the semi-honest oblivious transfer. However, currently, the best known black-box constructions under the same assumption require max(ROT, Oe(log2 n)) rounds. If ROT is a constant, the gap between non-black-box and black-box constructions can be a multiplicative factor log n. We close this gap by presenting a max(ROT, Oe(log n))-round black-box construction. We achieve this result by constructing constant-round 1-1 CCA-secure commitments assuming only blackbox access to one-way functions.

Dr. Rohit Chatterjee a postdoctoral researcher in cryptography (Research Fellow is the official designation) at the School of Computing at National University of Singapore, advised by Prof. Prashant Nalini Vasudevan. He completed his graduate studies in cryptography at the Computer Science & Engineering Department at Stony Brook University. He did his undergraduate and masters degrees (majoring in mathematics) at the Indian Institute of Science, Bangalore. 

June 2025