Last week, Open Whisper Systems was spotted testing the video calling feature in the Signal Private Messenger app's beta version on Android. Now, the company has officially announced that the video calling feature is now available (still in beta state) with the latest update to the communication app on both Android and iOS. The company says that the update also brings along new infrastructure for voice calls, which it claims, improves voice call quality as well. Users on iOS will further get CallKit functionality, which notably however impact the security offered by the app which is best known for user privacy.
Open Whisper Systems says that it will be rolling out the video calling feature in stages to receive feedback from users on different phones and networks to ensure "there are no surprises" when it is turned on by default. In order to make video calls, the feature is required to be enabled on both the caller and recipient's devices. To switch on the feature, users need to go to Settings > Advanced > Video calling beta in the app.
Enabling the new calling features on iOS further provides users with the option to use CallKit functionality that allows them to receive calls directly from the lockscreen itself. Notably, CallKit support also means that the app will sync the time period and the contact information of the calls with iCloud. This leaves the app vulnerable to leaking user information in the form of this meta data. If users want to protect this information as well, they will need to turn of CallKit integration via the Settings > Advanced > Use CallKit. Notably, CallKit integration is two-way, and will only be used if both parties have it enabled.
As Signal has previously found support from privacy icon like Edward Snowden, this vulnerability and dependence that comes along with the latest update should be noted by users. Speaking to Wired, Open Whisper says it is not certain if it will enable CallKit by default, or if it should be an opt-in feature. It could potentially label callers as Signal Users in CallKit to protect privacy, or have a privacy settings walkthrough to educate users of the pitfalls of CallKit.
"CallKit offers a native calling experience to VoIP apps like Signal. As well as being able to answer calls directly from your lock screen, you'll also see Signal calls in the system's 'Recent Calls' list. This is because iOS treats CallKit calls like any other call, however that also means some information will be synced to iCloud if enabled. This information includes who you called and how long you talked," the company said in its blog post on Tuesday.