CyLab Seminar: Sarah Scheffler
November 11, 2024
12:00 p.m. ET
Zoom or CIC room 4105, Panther Hollow
*Please note: this CyLab seminar is open only to partners and Carnegie Mellon University faculty, students, and staff.
Speaker:
Sarah Scheffler
Assistant Professor
Carnegie Mellon University
Talk Title:
Verifiable and Private Content Moderation for End-to-End Encryption
Abstract:
End-to-end encryption (E2EE) prevents service providers from directly accessing plaintext user content like messages or files, providing valuable privacy and security benefits to users of these services. However, those privacy protections also make it difficult for the service to perform content moderation to identify, label, monitor, or remove content that is offensive, harmful, or illegal. Some proposals have been made for doing content moderation under encryption in a privacy-preserving way, but these often require subtle adjustments to the security and privacy guarantees of E2EE. This talk will begin with a systematization of content moderation under E2EE, and will proceed to discuss two important and underexamined possibilities for content moderation in this setting that mitigate many of the privacy concerns inherent in E2EE moderation: verifiability of moderation, and measuring aggregate trends. For the verification component, we will discuss cryptographic protocols for (1) verifying approval of matchlists by external organizations, (2) guaranteed notification of detection, and (3) proof of non-membership of benign content in matchlists. For aggregate measurement, we will describe ongoing efforts with journalists to build ethical data donation models for E2EE messages that enable journalists to identify aggregate "trends" in E2EE messages without ever revealing individual message content, using a combination of differential privacy and secure multi-party computation over donated message embeddings.
This talk is based upon three works which were completed or are ongoing; this is joint work with Micha Gorelick, Palak Jain, Anunay Kulshrestha, Jonathan Mayer, and Madelyne Xiao.
Bio:
Sarah Scheffler is an Assistant Professor at CMU, joint between the Department of Engineering and Public Policy, and the Software and Societal Systems Department, and is a core faculty member of CyLab. Her research centers on applied cryptography and its intersection with policy, especially content moderation with verification and privacy, end-to-end encryption, compelled decryption, privacy-respecting and verifiable data journalism, and private and secure autonomous systems. She also does research in “pure” applied cryptography, including works on zero-knowledge proofs and multi-party computation. She holds a Ph.D. in computer science from Boston University. Prior to joining CMU in 2024 she was a postdoc at MIT’s Internet Policy Research Initiative, and in Princeton University’s Center for Information Technology Policy.