As you interact with the Lock screen’s passcode entry interface, you’ll notice that the number keys are always in the same place. This makes entering passcodes easier, but it also makes it effortless for nosy folks to glance over your shoulder and watch the numbers you dial in to unlock your device.
Here to help with this problem is a free jailbreak tweak called CodeScramber 12 by iOS developer eskimo_dev. As you might’ve already deduced from the tweak’s name, CodeScrambler 12 randomizes the locations of the passcode’s numeric keys every time you try to unlock your handset, as shown above.