Implement auto-lock feature for app on iOS

Question

i want to implement a secure timebased auto-lock function for my app (similar to the auto-lock-feature in 1password). The user can chose a passcode and a time period (1,2,3,5,10,30 minutes) after the lock is activated. Basically I could write a timestamp (encrypted) on my device and compare it with the current time of the next usage. If the delta is bigger than the chosen time period, the user has to enter the passcode. But this feature could be leavered out by changing the local time on the device. There must be a secure way (e.g. special system timer) to do that. So you can't lever out 1Password in this way. Any ideas?

Thanks a lot

Jürgen

Answer 1

Use:

[[UIApplication sharedApplication] setIdleTimerDisabled:YES];

Now set a timer:

  [NSTimer scheduledTimerWithTimeInterval:240 target:self selector:@selector(disableIdleTimer) userInfo:nil repeats:NO];

disableIdleTimer method set this:

[[UIApplication sharedApplication] setIdleTimerDisabled:NO];

Done!!

Answer 2

you should be using an Internet time server. They are using a standardized protocol called NTP. The iOS has built-in support for reading NTP server time, but this is not accessible for you as an application developer. Either you implement this yourself, or you could maybe use an open source library, like ios-ntp or HS NTP.