Signal expands encrypted group video calls to 40 people

Messaging app Signal can now support group video chats with 40 participants — up from five — and end-to-end encryption will still be intact. 

The nonprofit behind Signal announced the change on Wednesday; end-to-end encryption means only the participants in the call can view the messages or video. No one, including the messaging provider, government authorities, or hackers, can view the calls, unless a participant accepts them into the video session or they snatch your device. 

Signal is best known for offering end-to-end encrypted messaging. However, the developers behind the app only began working on encrypted group video chats last year during the height of the pandemic before rolling it out last December. 

Signal's new 40-participant cap is higher than some rival messaging apps. WhatsApp offers end-to-end encrypted video calls for up to eight participants, for example, while Apple’s FaceTime supports up to 32 people at once.

Zoom, on the other hand, lets you host an end-to-end encrypted video session with up to 200 participants, though users have to go out of their way to activate the encryption setting.  

If you’re hoping the Signal Foundation can expand the video calls beyond 40 participants, there’s good news: The nonprofit said this might one day be possible. 

In a blog post on Wednesday, the Signal Foundation explained that expanding the group video call function from five participants to 40 involved creating servers that can forward the video call to all participants without viewing or altering the data. Eventually, the Signal Foundation settled on writing the computer code for the server from scratch using the programming language Rust. 

“It has now been serving all Signal group calls for 9 months, scales to 40 participants with ease (perhaps more in the future),” the nonprofit wrote. The encryption keys necessary to secure the calls also continue to come from user devices, not from the servers.

"When a client joins the call, it generates a key and sends it to all other clients of the call over Signal messages," the Signal Foundation added. "Whenever any user joins or leaves the call, each client in the call generates a new key and sends it to all clients in the call. It then begins using that key 3 seconds later."