With the vault setting “Unlock Duration”, you can specify for how long you want your vault to stay unlocked when idle. The following options are:
Let iOS Decide Automatically
The default option is “Let iOS Decide Automatically”. Accessing Cryptomator via the Files app is possible via a so-called File Provider Extension. This extension has limited capabilities, e.g., it has a lower memory limit than regular apps. To free up memory, iOS may terminate Cryptomator at any time, which is basically the same as locking the vault since the key is held in memory.
This option has two consequences:
There is no guarantee for how long your vault stays unlocked. Of course, while you’re accessing your vault, it’s highly unlikely that Cryptomator gets terminated.
You’re responsible for locking your vault manually. Or if that’s not a concern of yours, you can just let iOS decide when Cryptomator is getting terminated.
In order to have a guarantee that your vault stays unlocked for a certain amount of time, the other options are available. By using one of these options, a copy of your key needs to be stored in the iOS keychain, as long as your vault is unlocked.
E.g., if you choose “1 Hour” and Cryptomator gets terminated by iOS within that time frame, your vault can automatically be unlocked again using the key from the iOS keychain. If the selected time frame has passed, the key will be removed from the iOS keychain and your vault will get automatically locked.
If you choose the “Indefinite” option, your vault will be kept unlocked until you have manually locked it.