The original title is "Signal Protocol: A Technical Deep Dive into Modern Encrypted Messaging"

Short summary

Signal Protocol powers secure messaging for billions daily through X3DH key agreement (enabling async handshakes) and Double Ratchet encryption combining DH and symmetric ratcheting for per-message keys with AES-256-CBC and HMAC-SHA256. Key features include graceful out-of-order handling, efficient group messaging via Sender Key, and Sealed Sender—hiding message senders even from the server.

• •X3DH key agreement enables asynchronous messaging where parties don't need simultaneous online presence
• •Double Ratchet provides continuous forward and future secrecy through DH ratchet (asymmetric) and symmetric ratchet (per-message)
• •Group messaging uses Sender Key for O(1) efficiency, out-of-order messages handled via skipped key windows, Sealed Sender hides senders from servers

Generated with AI, which can make mistakes.