Hecate: Abuse Reporting in Secure Messengers with Sealed Sender

Speaker: Rawane Issa , Boston University

Date: Wednesday, May 04, 2022

Time: 3:00 PM to 4:00 PM Note: all times are in the Eastern Time Zone

Public: Yes

Location: 32-D463 (Star)

Event Type: Seminar

Room Description:

Host: Srinivas Devadas, CSAIL

Contact: Kyle L Hogan, klhogan@csail.mit.edu

Relevant URL:

Speaker URL: None

Speaker Photo:

Reminders to: seminars@csail.mit.edu, ra1issa@bu.edu

Reminder Subject: TALK: Hecate: Abuse Reporting in Secure Messengers with Sealed Sender


End-to-end encryption provides strong privacy protections to billions of people, but it also compli-
cates efforts to moderate content that can seriously harm people. To address this concern, Tyagi et
al. [CRYPTO 2019] introduced the concept of asymmetric message franking (AMF) so that people
can report abusive content to a moderator, while otherwise retaining end-to-end privacy by default and
compatibility with anonymous communication systems like Signal’s sealed sender.
In this work, we provide a new construction for asymmetric message franking called Hecate that
is faster, more secure, and introduces additional functionality compared to Tyagi et al. First, our
construction uses fewer invocations of standardized crypto primitives and operates in the plain model.
Second, on top of AMF’s accountability and deniability requirements, we also add forward and backward
secrecy. Third, we combine AMF with source tracing, another approach to content moderation that has
previously been considered only in the setting of non-anonymous networks. Source tracing allows for
messages to be forwarded, and a report only identifies the original source who created a message. To
provide anonymity for senders and forwarders, we introduce a model of AMF with preprocessing whereby
every client authenticates with the moderator out-of-band to receive a token that they later consume
when sending a message anonymously.

Research Areas:
Security & Cryptography

Impact Areas:

See other events that are part of the CSAIL Security Seminar Series 2022-2023.

Created by Kyle L Hogan Email at Thursday, April 21, 2022 at 1:53 PM.