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. My research is focused on applied cryptography (and more recently on theoretical cryptography). Previously, I was also interested in algorithms, computer graphics, and database systems. I've spent the fall and spring semesters of 2023-2024 visiting Geoffroy Couteau at IRIF. Before MIT, I was an undergrad at Brown University.
In my spare time I like to make art, cycle, and run around the Charles River.

GitHub · CV

Recent projects
Constrained PRFs from weaker assumptions
Constrained PRFs (CPRFs) have many applications. Until recently, we only knew how to construct CPRFs for simple constraint predicates under standard assumptions. We examine the case of inner product predicates (which give rise to a number of other useful predicates such as predicates described by constant-degree polynomials). We show that it is possible to construct constraint-hiding CPRFs for inner product predicates (1) unconditionally in the random oracle model, (2) under DDH, and (3) from the minimal assumption that one-way functions exist under certain restrictions. Previously, CPRFs for inner product constraints were only known from the DCR and LWE assumptions, or from non-standard assumptions. Our constructions are also the first to be concretely practical.

Paper · Slides · Code
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

I like to take photos when I travel.

My favorite work music:
Cool links I've come across:
© 2024 Sacha Servan-Schreiber