Tor & Encryption about airbitz-core HOT 2 OPEN

Most of this stuff is iOS-specific. The Airbitz wallet core runs on iOS, Android, and desktop *nix, so we can't use any ObjectiveC or Apple-specific technologies in there.

The Airbitz wallet talks to three different types of servers. The login server has an HTTP/REST interface, and handles username lookup on first login, as well as checking the PIN on each PIN login, handling 2fa, and a few other chores like that. This server is zero-knowledge, meaning it doesn't actually know the username, PIN, or any other personally-identifiable data, just hashes. If the server goes down, users can still access their wallets locally via password login.

Airbitz connects to the Bitcoin network via libbitcoin servers. These servers use a ZeroMQ-based interface, and the libbitcoin project has efforts underway to enable Tor for these connections. If/when that work comes to fruition, we will most likely adopt it.

Airbitz also uses Git servers to sync files between devices. We use the HTTPS transport currently.

The libbitcoin idea for Tor is to run ZeroMQ over a SOCKS proxy, which then provides the Tor routing. This works great on Android, where the Tor client can literally be a separate process. On iOS we will have to host the Tor client inside our app's main process, but this shouldn't be too much work (just rename their main() function to startTor() or such and call it on a separate thread). Once we have a Tor proxy working for libbitcoin, we can probably run the other two types of connections over that as well.

We encrypt all our own data using AES256. We don't write anything to disk without encryption, aside from a few device-only files. These files are synced between devices using Git, as mentioned earlier. The username and password, when combined with salts stored on the login server, derive the first-level encryption keys for this data. These first-level keys then unlock the second-level keys, which unlock the data itself. This way, we can change the username and password without re-encrypting everything - we just need to re-encrypt the second-level keys. The second-level keys can also be unlocked using the PIN.

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Thanks for the response. Sorry for the late reply.

from airbitz-core.