~/talk

Private Calling at WhatsApp

on YouTube 19m
Talkat RTC @Scale 2022 · on Wednesday, 2022-02-16· [networking, security]

speaker

name:Xi Deng
links:none on file

resources

video:https://youtu.be/1z17jOhJNsU
slides:none on file

summary

WhatsApp builds private calling for 2 billion users handling 15 billion minutes a day using a client-centric architecture that keeps call state on clients and keeps signal servers stateless with no PII. 1:1 calls use SRTP with a per-call master secret exchanged over an E2EE Signal‑like channel and per-device secrets for multi‑device isolation. P2P is used when safe; strangers force relays. Group calls use SFUs, a centralized transient state to resolve conflicts, and session key rotation with a SFU + session key rotation generator to rekey on membership changes for scalability and privacy.

AI-written summary · about

chapters (6)

  1. 0:00Introduction
  2. 0:54Understanding Privacy
  3. 4:19Private OnetoOne Call
  4. 9:47Challenges
  5. 14:02Group Call
  6. 17:52Recap

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