Ling Ren

Research

Currently, my research group focuses on fault-tolerant consensus (what most people call blockchain), distributed cryptography, and cryptography for privacy protection. Here are some of our recent works.

• An adaptively secure BLS threshold signature. 

• A weighted threshold signature via inner product argument.  

• Practical private information retrieval (PIR), batch PIR, and amortized sublinear stateful PIR protocols.

• New protocols for distributed cryptography (mostly) in asynchrony and without trusted setup: data dissemination, reliable broadcast, verifiable information dispersal, verifiable secret sharing, randomness beacon,  distributed key generation, and q-SDH trapdoor generation. 

• 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. 

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

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

I am thankful for the generous support of the National Science Foundation, Google, Meta, VMware, and Protocol Labs on our research.  

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

Cryptography for privacy

Muhammad Haris Mughees, Sun I, and Ling Ren. Simple and Practical Amortized Sublinear Private Information Retrieval. Preprint 2023.

Muhammad Haris Mughees and Ling Ren. Vectorized Batch Private Information Retrieval. S&P 2023. Code

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

Hao Chen, Ilaria Chillotti, and Ling Ren. Onion Ring ORAM: Efficient Constant Bandwidth Oblivious RAM from (Leveled) TFHE.  CCS 2019.

Ling Ren,  Christopher Fletcher, Albert Kwon,  Marten van Dijk, 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 and Ling Ren. Adaptively Secure BLS Threshold Signatures from DDH and co-CDH. Preprint 2023.

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, Zhuolun Xiang, Lefteris Kokoris-Kogias, and Ling Ren. Practical Asynchronous High-Threshold Distributed Key Generation and Distributed Polynomial Sampling. Usenix Security 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, Irene Miriam Isaac, and Ling Ren. SPURT: Scalable Distributed Randomness Beacon with Transparent Setup. S&P 2022.

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

Consensus

Dahlia Malkhi, Atsuki Momose, and Ling Ren. Towards Practical Sleepy BFT. CCS 2023. 

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