Another good option—this one for iPhone users only—is Avira Vault (for iOS), which can protect photos, passwords, and credit-card details. Although the base version is free, it limits your storage to 100 files, one credit card, and three passwords. To exceed that, you need to pay $4 per month. Although the app is only available for iOS, you can find a related Android app: Avira AppLock+ (for Android). Instead of creating a vault, this one lets you add extra PIN code protection to specific apps, such as your photo manager or your instant messenger.