Welcome to my digital corner!

Sacha Servan-Schreiber
3s [at] mit.edu

I'm a Ph.D. student at MIT CSAIL, advised by Srini Devadas. Before MIT, I was an undergrad at Brown University. My research is focused on applied cryptography. In my spare time I like to make art, cycle, and run around the Charles river.

GitHub · CV

Photo by Jules Drean
Recent projects
Access control for function secret sharing
Function secret sharing (FSS) has seen many applications in privacy-preserving systems. An important feature in these systems is the ability to enforce access control privately. We formalize this notion and provide several constructions for access control in FSS. We evaluate several applications of access control for FSS, including PIR with access control and faster anonymous communication.

Paper · Slides · Code

Talk given at: IRIF laboratory at the CNRS and University of Paris Cité, IEEE S&P.
A faster, more robust, scalable mix-net for anonymous broadcast
Mix-nets offer great scalability properties and can be used to instantiate anonymous broadcast (and communication) efficiently. We design and build Trellis, a new mix-net based anonymous broadcast system that offers: (1) concrete efficiency, (2) network robustness in the face of malicious servers, (3) scalability with added servers, and (4) security even when a majority of mix servers are malicious.

Paper · Slides · Code
Making Tor faster with Multi-hop Overlay Routing
Tor can be significantly slower compared to regular browsing largely due to the way in which Tor routes traffic over the internet. Tor requires routing packets through multiple relays forming a "circuit." Traffic congestions between relays on a Tor circuit can lead to delays, increasing latency, and hindering user experience. ShorTor is an overlay for the Tor network which can help find shorter paths between relays using a trick deployed by major CDNs. ShorTor reduces latency between relays, is incrementally deployable, and minimally impacts the security of Tor.

Paper · Slides · Code
Private Approximate Nearest Neighbor Search
How do you find and retrieve similar items (a.k.a. nearest neighbors) from a remote database without revealing what you're looking for? We present Preco, an efficient privacy-preserving approximate nearest neighbor search protocol between a client and a remote database (replicated on two non-colluding servers). Preco takes into consideration the privacy of the client and the database. With Preco, clients can efficiently query for nearest neighbors in the database without the high communication overhead of prior work.

Paper · Slides · Code

Talk given at: Berkeley University, IEEE S&P.
High-bandwidth Anonymous Broadcasting
How do you broadcast high-bandwidth documents (e.g., video leaks) anonymously, even when the entire network is monitored?
We design and build Spectrum, a system for anonymously broadcasting large files over an untrusted network without leaking any metadata; even in the presence of a powerful network adversary.

Paper · Slides · Code

Talk given at: Cornell University, Northeastern University, NSDI.
Selected publications
© 2023 Sacha Servan-Schreiber