Signal is generally viewed as the most secure encrypted communications app. So secure, that even the US Senate has approved it for staff use. And, to keep privacy experts on its side, Open Whisper Systems (the non-profit behind the app) has kept Signal open source and peer-reviewed. But, the developer is having to juggle robust privacy with all the popular features a chat app is expected to provide in this day and age. It's proven a tricky balancing act -- particularly in regards to access to user contacts. Just like its (now encrypted) rivals, Signal asks to import your phone contacts in order to tell you who's using the app. For the stricter privacy advocates, that's always been a niggling issue. But, Signal claims it has a fix. With its latest test, the app is trialling a completely private contact discovery service.