Ling Ren

32 Vassar St, G890

Cambridge, MA, 02139


I am a graduate student at MIT CSAIL. My advisor is Professor Srinivas Devadas. I do research in applied cryptography, computer security and hardware. My research has been as theoretical as asymptotically better algorithms, and as practical as taping out a processor. I received my Bachelor's degree from Tsinghua University in Beijing, China.


Research

I worked on Oblivious RAM (ORAM) algorithms and hardware implementations. In collaboration with Princeton, we taped out in 32nm technology a 25-core secure processor with an on-chip Path ORAM controller that encrypts, shuffles and integrity-verifies external memory. Here are the paper and source code. We invented Onion ORAM, the first ORAM construction with O(1) bandwidth blowup, circumventing a well-known logarithmic lower bound. Our follow-up paper discusses how we can and cannot circumvent the bound.

Recently, I have been working on consensus and blockchains, including efficient Byzantine consensus and its application to a new blockchain protocol called Solida. The above work started while I was interning at VMware Research Group, where I have been fortunate to work with Dr. Dahlia Malkhi and Dr. Ittai Abraham. I am also studying techniques for more egalitarian blockchains, such as proof of space and ASIC resistant hash functions.

I have also worked on a physical unclonable function based on LPN and improved LPN algorithms.


Selected Publications and Manuscripts

For a full list, see my Google Scholar page or CV.

Ittai Abraham, Srinivas Devadas, Danny Dolev, Kartik Nayak, and Ling Ren. Efficient Synchronous Byzantine Consensus. Preprint.

Ittai Abraham, Dahlia Malkhi, Kartik Nayak, Ling Ren, and Alexander Spiegelman. Solida: A Blockchain Protocol Based on Reconfigurable Byzantine Consensus. In International Conference on Principles of Distributed Systems (OPODIS), 2017.

Srinivas Devadas, Ling Ren and Hanshen Xiao. On Iterative Collision Search for LPN and Subset Sum. Theory of Cryptography Conference (TCC), 2017.

Ling Ren and Srinivas Devadas. Bandwidth Hard Functions for ASIC Resistance. Theory of Cryptography Conference (TCC), 2017. Slides

Ling Ren, Christopher Fletcher, Albert Kwon, Marten van Dijk, and Srinivas Devadas. Design and Implementation of the Ascend Secure Processor. IEEE Transactions on Dependable and Secure Computing (TDSC), 2017.

Ittai Abraham, Christopher Fletcher, Kartik Nayak, Benny Pinkas, and Ling Ren. Asymptotically Tight Bounds for Composing ORAM with PIR. International Workshop on Public Key Cryptography (PKC), 2017.

Ling Ren, Srinivas Devadas. Proof of Space from Stacked Expanders. Theory of Cryptography Conference (TCC), 2016. Slides

Charles Herder, Ling Ren, Marten van Dijk, Meng-Day Yu, and Srinivas Devadas. Trapdoor Computational Fuzzy Extractors and Stateless Cryptographically Secure Physical Unclonable Functions. IEEE Transactions on Dependable and Secure Computing (TDSC), 2016

Srinivas Devadas, Marten van Dijk, Christopher Fletcher, Ling Ren, Elaine Shi, and Daniel Wichs. Onion ORAM: A Constant Bandwidth Blowup Oblivious RAM. Theory of Cryptography Conference (TCC), 2016. Slides

Ling Ren, Christopher Fletcher, Albert Kwon, Emil Stefanov, Elaine Shi, Marten van Dijk, and Srinivas Devadas. Constants Count: Practical Improvements to Oblivious RAM. USENIX Security, 2015.

Christopher Fletcher, Ling Ren, Albert Kwon, Marten van Dijk, Emil Stefanov, Dimitrios Serpanos, and Srinivas Devadas. A Low-Latency, Low-Area Hardware Oblivious RAM Controller. Symposium on Field-programmable Custom Computing Machines (FCCM), 2015.

Christopher Fletcher, Ling Ren, Albert Kwon, Marten van Dijk, and Srinivas Devadas. Freecursive ORAM: [Nearly] Free Recursion and Integrity Verification for Position-based ORAMs. Architectural Support for Programming Languages and Operating Systems (ASPLOS), 2015. Slides

Emil Stefanov, Marten van Dijk, Elaine Shi, Christopher Fletcher, Ling Ren, Xiangyao Yu, and Srinivas Devadas. Path ORAM: An Extremely Simple Oblivious RAM Protocol. Computer & Communications Security (CCS), 2013. Best Student Paper Award.

Ling Ren, Xiangyao Yu, Christopher Fletcher, Marten Van Dijk, and Srinivas Devadas. Design Space Exploration and Optimization of Path Oblivious RAM in Secure Processors. International Symposium on Computer Architecture (ISCA), 2013. Slides

Ling Ren, Xiaoming Chen, Yu Wang, Chenxi Zhang, and Huazhong Yang. Sparse LU Factorization for Parallel Circuit Simulation on GPU. Design Automation Conference (DAC), 2012.


Teaching

Teaching Assistant, 6.046J Design and Analysis of Algorithms, Spring 2015. Available on MIT OpenCourseWare.

Co-instructor, 6.046J Design and Analysis of Algorithms, fall 2017.