Disclaimer
All the information is my interpretation of the iOS Security Guide
Slide 4
Slide 4 text
Effaceable Storage
• how to truly erase something from an SSD?
(source: http:/
/lwn.net)
• Apple's solution: small chunk of memory not subject to wear leveling
Slide 5
Slide 5 text
Metadata
• encrypted with random key created on install
• not for confidentiality
• in Effaceable Storage
• !
• ✅ FBI knows that one
Slide 6
Slide 6 text
Files
The content of a file is encrypted with a per-file key, which is wrapped
with a class key and stored in a file’s metadata
— iOS Security Guide
FBI needs the file key ( )
1. ✅ — the file they want to decrypt
2. ✅ — the file system key
3. ❌ — the mysterious class key
Slide 7
Slide 7 text
Class Key
The class key is protected with the hardware UID and, for some classes,
the user’s passcode.
— iOS Security Guide
• hardware UID: AES 256-bit key fused into the application processor
• No software or firmware can read them directly
• see only the results of encryption or decryption operations
performed by dedicated AES engines
Slide 8
Slide 8 text
Class Key, contd.
1. ❌ ❌ — !"
2. #
3. ❌
4. , , ..., ? 10000 possibilities — !$
5. how to we access the AES engine?
Slide 9
Slide 9 text
iOS Kernel*
✅ ✅ ❌
So the only protection* is that the FBI can't easily run code in kernel
mode.
*) on older devices (up until iPhone 5C)
Slide 10
Slide 10 text
So why
!"?
Slide 11
Slide 11 text
Ways to get around it
• jail break
• prevent SSD from being erased & try
• crypto vulnerability
• acid + focussed ion beam ?
• reboot early & try ?
• ???