You can store data on local disk using NSArchiver and NSUnarchiver in this way:
// set your image in cache
NSData *imgData = [NSKeyedArchiver archivedDataWithRootObject:myImage];
NSUserDefaults *defaults = [NSUserDefaults standardUserDefaults];
[defaults setObject:imgData forKey:@"img_01"];
[defaults synchronize];
//get your image from cache
NSData *imgData = [[NSUserDefaults standardUserDefaults] objectForKey:@"img_01"];
myImage = [NSKeyedUnarchiver unarchiveObjectWithData:imgData];
Reference apple here: http://goo.gl/XH2o2
hope this helps.