Also, Obscura can collect metadata on when you use the service, how much data you send/receive, etc.
Even if Mullvad doesn't do it, someone else might. Mullvad is, I expect, now a valuable target because it is the VPN service of choice for so many people concerned with security. Does Mullvad have the budget and expertise to protect itself against determined, highly-resourced attackers?
Finally, is it possible for a third party, intercepting traffic between Obscura and Mullvad, to identify the public key used to encrypt it? I don't think so - the only way to validate a signature is with both keys; that's kind of the point. But maybe there is an attack I'm unaware of?
Even if Mullvad doesn't do it, someone else might. Mullvad is, I expect, now a valuable target because it is the VPN service of choice for so many people concerned with security. Does Mullvad have the budget and expertise to protect itself against determined, highly-resourced attackers?
Finally, is it possible for a third party, intercepting traffic between Obscura and Mullvad, to identify the public key used to encrypt it? I don't think so - the only way to validate a signature is with both keys; that's kind of the point. But maybe there is an attack I'm unaware of?