Fortress is a Stellar Vault used to store your Lumens offline without ever connecting to the internet. It uses QR Codes to communicate with a read-only mobile dumb client which can submit transactions to the network once they've been signed by the vault app. It also reads the current transaction sequence from the mobile client in order to generate valid transactions so it acts as a two way visual QR Code communicator keeping the vault isolated from external connections giving you total peace of mind. The mobile client in read-only mode can show balances to keep you updated on your assets since the vault can not connect to the main network.
In other words, there will be two apps, one local -the vault- to be used on air-gapped devices, and one mobile which will connect to the network in order to check balances and submit transactions once signed by the vault.
