iOS Internals · Inside iOS · Lesson 5 of 5

Challenge: The Free Gems Offer

Check a website's free-gems offer for your cousin and explain what it would break.

Case brief

Your cousin Maya, who's 14, plays a game called Gem Quest on an iPhone X she inherited from her dad. It's still on iOS 16. A video sent her to a website promising unlimited free gems. She asks you to check it before she tries it. The site says:

• Step 1: Download the GemHack profile, then go to Settings and trust the developer "Sunrise Logistics Ltd" so GemHack will open.
• Step 2: GemHack opens Gem Quest's save file and rewrites your gem count.
• Step 3: If Step 2 fails, use our checkm8 tool. "Works great on iPhone X, and Apple can't patch it."

GemHack isn't in the App Store. Maya lives in the US. She points out that the site has thousands of five-star comments.

Rewriting the save file

Suppose Maya did install GemHack. Step 2 says it will open Gem Quest's save file and change the number of gems.

Gem Quest keeps its save file inside its own folder on the phone. GemHack and Gem Quest come from different developers, and GemHack isn't a picker or the share sheet. Think about what iOS gives each app when it's installed, and whether one app can walk into another's.

The checkm8 pitch

Step 3 is the site's backup plan. It wants Maya to connect her iPhone X to a computer and run a checkm8 tool, which would jailbreak the phone so GemHack can reach other apps' data.

Maya reads the line "Apple can't patch it" as a good sign. To her, it sounds like the tool is so solid that even Apple has given up on it. She also notes that her iPhone X is on Apple's chip list for the bug.

The bigger picture

You talk Maya out of GemHack, and she deletes the downloaded profile. Then you look at her phone more closely. Her iPhone X can't install anything newer than iOS 16. It has an A11 chip, and she uses it for school email and messaging friends.

Her dad says the phone still works perfectly, so there's no need to change anything. He'd like a reason before spending money on a new one.