{"guid":"38c50a6f-72a3-5c1a-9fc2-9cb6e60db185","title":"Joining the conversation: balancing privacy with usability for encrypted messages","subtitle":null,"slug":"matrix-conf-2025-72720-joining-the-conversation-balancing-privacy-with-usability-for-encrypted-messages","link":"https://cfp.2025.matrix.org/matrix-conf-2025/talk/VLF9QQ/","description":"Being able to read the conversation in a room before you joined is a critical feature for some usecases, but end-to-end encryption makes it tricky to implement.\n\nIn this technically-focussed talk, we'll cover the challenges behind implementing \"history sharing\", why previous attempts in this area failed, and how we solved those problems with minimal impact on the security or efficiency of the protocol.\n\nThe Element Crypto team have been working on [MSC4268](https://github.com/matrix-org/matrix-spec-proposals/pull/4268), aka \"Sharing room keys for past messages\". We'll talk about why this is difficult from the cryptographic perspective, and discuss the architecture behind the implementation.\n\nLicensed to the public under https://creativecommons.org/licenses/by-sa/4.0/","original_language":"eng","persons":["Richard van der Hoff"],"view_count":72,"promoted":false,"date":"2025-10-17T15:00:00.000+02:00","release_date":"2025-10-17T00:00:00.000+02:00","updated_at":"2026-04-20T19:30:05.342+02:00","tags":["72720","2025","matrix-conf-2025","Security \u0026 Encryption","Alan Turing","matrix-conf-2025-eng","matrix-conf-2025","Day 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