Out of Band Authentication in Group Messaging - Computational, Statistical, Optimal

Explore a presentation from Crypto 2018 on out-of-band authentication in group messaging, focusing on computational, statistical, and optimal aspects. Delve into the paper by Lior Rotem and Gil Segev, which addresses end-to-end encrypted messaging, man-in-the-middle attacks, and user-to-user settings. Examine the group setting, correctness and security measures, and the proposed computationally-secure protocol. Investigate concurrent non-malleable commitments, statistical lower bounds, and protocol structures. Gain insights into the challenges and solutions for secure group messaging authentication.

Intro
Major Effort: E2E-Encrypted Messaging
Man-in-the-Middle Attacks
The User-to-User Setting
User-to-User Bounds
This Talk: The Group Setting
Our Contributions
Correctness & Security
The Naïve Protocol
Our Computationally-Secure Protocol
Example: One Possible Attack
Concurrent Non-Malleable Commitments
Our Statistical Lower Bound
Protocol Structure
Understanding H(E)