New techniques for theory and practice of distributed cryptographic systems

Das, Sourav

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https://hdl.handle.net/2142/129824 Copy

Description

Title

New techniques for theory and practice of distributed cryptographic systems

Author(s)

Das, Sourav

Issue Date

2025-06-18

Doctoral Committee Chair(s)

Ren, Ling

Committee Member(s)

• Gupta, Indranil
• Miller, Andrew
• Cachin, Christian
• Shoup, Victor

Department of Study

Siebel School Comp & Data Sci

Discipline

Computer Science

Degree Granting Institution

University of Illinois Urbana-Champaign

Degree Name

Ph.D.

Degree Level

Dissertation

Keyword(s)

Distributed Computing, Cryptography, Distributed Cryptographic Systems

Abstract

Cyber-attacks leveraging single points of failure increasingly threaten digital privacy and critical infrastructures. Distributed cryptographic systems counter these attacks on single points of failure by distributing trust and workload while ensuring privacy, security, and availability, even if a large fraction of machines are compromised. As cyber-attacks become more sophisticated and critical infrastructures evolve to meet modern requirements, it is increasingly crucial to design secure, robust, and scalable distributed cryptographic systems that account for modern adversarial capabilities, infrastructures, and emerging applications. In this thesis, I study building efficient distributed cryptographic systems -- both asymptotically and concretely -- that provide rigorous cryptographic security against modern adversaries and address contemporary application needs. Toward this goal, I have worked on two key topics focusing on the design and implementation of secure, scalable, and trustless (i) distributed and threshold cryptographic protocols and (ii) Byzantine fault-tolerant (BFT) algorithms and distributed systems. Moreover, this thesis is motivated by the need for threshold cryptography in contemporary applications and their practical deployments. More precisely, I have designed efficient protocols for fundamental building blocks for asynchronous distributed cryptographic primitives, such as asynchronous reliable broadcasts, asynchronous verifiable information dispersal, and Verifiable Secret Sharing for synchronous and asynchronous networks. For many of these primitives, protocols I designed for this thesis achieve near-optimal communication complexity, while maintaining their practical efficiency. This thesis also proposes practical constructions for both distributed key generation protocols for asynchronous networks and a threshold signature scheme that supports arbitrary weights and simultaneously supports arbitrary thresholds. Compared to prior work with similar properties, our protocol achieves significant performance improvements and sometimes asymptotic improvements by a factor linear in the number of parties in the protocol. Finally, I proposed the first-ever adaptive security proof of threshold Boneh-Lynn-Sacham~(BLS) and threshold Schnorr signature, assuming the standard hardness assumption.

Graduation Semester

2025-08

Type of Resource

Thesis

Handle URL

https://hdl.handle.net/2142/129824

Copyright and License Information

Copyright 2025 Sourav Das

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