I'm not clear on the technical details here.

> Obscura’s servers relay your connection to exit servers but can never decrypt your traffic.

Doesn't that rely on us trusting that the server runs the code they claim it does? Or is there a way to prove that their server can't get the decryption key (i.e. by proving that it's not possible for them to switch the final hop, or add undisclosed hops in between)?