Facebook has introduced a new feature - mysteriously called "secret conversations" - for its Messenger mobile app.

That name is just fancy talk for end-to-end encryption. The company just started testing the security feature by making it available to a select group of people and only for select conversations, with the promise that it will become more widely available this summer. Facebook won't turn it on straightaway for everyone, because it's "putting a lot of thought into the design and implementation of this feature".

In the wake of recent mass surveillance concerns, Facebook heard users asking for additional safeguards, so it began actively developing end-to-end encryption for Messenger. Keep in mind Facebook-owned WhatsApp introduced end-to-end encryption in April, but the feature works for all users and all messages, rather than an opt-in, conversation-by-conversation basis.

Messages sent using end-to-end encryption won't support GIFs and videos, but Facebook users will be able to set timers on messages, enabling the threads to self-destruct after a set amount of time, just like snaps in Snapchat. Messenger's encryption is also based on Open Whisper System Signal Protocol, which is whistleblower Edward Snowden's preferred means of encryption.

Facebook's "secret conversations" also only works from one phone, tablet, or computer. WhatsApp, similarly, can only work on one device at a time. This setup means Facebook won't have to give out unique encryption keys to multiple devices. You can read about the technical details here.

So, Friday's announcement is a small step, but it's a step in the right direction.

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