Ling Ren

Research

Currently, my research group focuses on threshold/distributed cryptography, cryptography for privacy protection, and fault-tolerant consensus (what most people call blockchain). I am thankful for the generous support of the National Science Foundation, Google, Meta, VMware, and Protocol Labs on our research.  Here are some of our recent works.

• Granular synchrony, a new network timing model that unifies the classic synchrony, partial synchrony, and asynchrony models. Here is a talk. 

• A method to threshold cryptography secure against adaptive corruptions. We have applied it to threshold BLS signature, Schnorr signature, and El Gamal decryption.  

• OnionPIR, a practical single-server Private Information Retrieval (PIR) protocol (updated draft and implementation in 2025). 

• Stateful PIR with practical efficiency and optimal space-time tradeoff.    

• Distributed cryptography in asynchrony with practical efficiency and no trusted setup: data dissemination, reliable broadcast, verifiable information dispersal, verifiable secret sharing, distributed key generation, and q-SDH trapdoor generation. 

• Simple and practical security analysis for Nakamoto consensus. This blog post gives an informal walk-through.

• Byzantine consensus with dynamic participation. This is one of the most prominent novel features of Nakamoto consensus. See this blog post and this talk for details. 

• Byzantine consensus with minority faults: foundational algorithm, prototype system, and answer to the long-standing open problem on its optimal communication complexity.

Selected Publications  (For a full list, see my Google Scholar page.)

Cryptography for privacy

Zhikun Wang and Ling Ren. Single-Server Client Preprocessing PIR with Tight Space-Time Trade-off. Eurocrypt 2025. 

Ling Ren, Muhammad Haris Mughees, and Sun I. Simple and Practical Amortized Sublinear Private Information Retrieval using Dummy Subsets. CCS 2024. Code

Ananya Appan, David Heath, and Ling Ren. Oblivious Single Access Machines. CCS 2024.

Muhammad Haris Mughees, Hao Chen, and Ling Ren. OnionPIR: Response Efficient Single-Server PIR. CCS 2021. Original and updated code

Ling Ren,  Christopher Fletcher, Albert Kwon,  Marten van Dijk, and Srinivas Devadas. Design and Implementation of the Ascend Secure Processor. TDSC 2017. Code

Emil Stefanov, Marten van Dijk, Elaine Shi, Christopher Fletcher, Ling Ren, Xiangyao Yu, and Srinivas Devadas. Path ORAM: An Extremely Simple Oblivious RAM Protocol. CCS 2013. Best Student Paper. Top Picks in Hardware Embedded Security. CCS Test-of-Time Award.

Distributed and threshold cryptography

Sourav Das, Zhuolun Xiang, Alin Tomescu, Alexander Spiegelman, Benny Pinkas, and Ling Ren. Verifiable Secret Sharing Simplified. S&P 2025. Code

Sourav Das and Ling Ren. Adaptively Secure BLS Threshold Signatures from DDH and co-CDH. Crypto 2024.

Sourav Das, Philippe Camacho, Zhuolun Xiang, Javier Nieto, Benedikt Bünz, and Ling Ren. Threshold Signatures from Inner Product Argument: Succinct, Weighted, and Multi-threshold. CCS 2023. Code

Sourav Das, Tom Yurek, Zhuolun Xiang, Andrew Miller, Lefteris Kokoris-Kogias, and Ling Ren. Practical Asynchronous Distributed Key Generation. S&P 2022. Code

Sourav Das, Zhuolun Xiang, and Ling Ren. Asynchronous Data Dissemination and Its Applications. CCS 2021. Best Paper Runner-up. 

Consensus

Neil Giridharan, Ittai Abraham, Natacha Crooks, Kartik Nayak, and Ling Ren. Granular Synchrony. DISC 2024.

Atsuki Momose and Ling Ren. Constant Latency in Sleepy Consensus. CCS 2022. 

Dongning Guo and Ling Ren. Bitcoin's Latency--Security Analysis Made Simple. AFT 2022. Bitcoin Research Prize. 

Atsuki Momose and Ling Ren. Optimal Communication Complexity of Authenticated Byzantine Agreement. DISC 2021.

Ittai Abraham, Kartik Nayak, Ling Ren, and Zhuolun Xiang. Good-case Latency of Byzantine Broadcast: a Complete Categorization. PODC 2021.

Ittai Abraham, Dahlia Malkhi, Kartik Nayak, Ling Ren, and Maofen Yin. Sync HotStuff: Simple and Practical Synchronous State Machine Replication, S&P 2020. Code