Q: Why should I trust Crosspass?
Crosspass has two components: the Crosspass server and the Crosspass mobile app. You should not trust any server with your passwords, including the Crosspass server. For this reason, the Crosspass server never sees your passwords or private notes.
The job of the Crosspass server is to relay encrypted data between the two phones in order to allow them to communicate peer-to-peer. Only the two Crosspass mobile apps can decrypt the blobs.