Requires the same level of trust as about any encryption tech these days. If it’s super secret/sensitive information you wish to protect, you probably shouldn’t be connected to the internet whatsoever, nor using anybody else’s software solution, regardless of how they are vetted. It’s a sad state of affairs, but it is where we are. I do not personally know or have any stake in this organization. I just found this while looking for a way to sync grocery store lists, etc between two linux boxes. I don’t own or use a smartphone, and cannot speak to this apps security is such a fundamentally compromised environment.