How does Apple handle deleted data on their iPhones?

Flash Storage does not use the TRIM function of SATA SSD drives to overwrite the data when it is deleted. This is due to the limited writes that are inherent in Flash storage and the drive would quickly fail if it was constantly zeroing data when a file is deleted or moved.

For that reason, Apple relies on encryption where any data that could be recovered is unreadable with the hash of the key stored in the Secure Enclave. Maybe this information will be helpful to you.

Data Protection overview - Apple Support

Protecting user data in the face of attack - Apple Support

Sealed Key Protection (SKP) - Apple Support

To learn more about the AES-256 encryption used:

https://www.progress.com/blogs/use-aes-256-encryption-secure-data

"How does Apple handle deleted data on their iPhones?: I'm doing a research project on different storage methods of mobile devices, and I am having trouble finding information on how apple handles storage. [...]"

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Recovering Deleted iPhone Items:

If not backed up in any manor (i.e. iCloud Backups or Duplication), then they'd be gone. As an example, here is how to go about recovering deleted photos:

Troubleshooting Lost Photos:

Having no backup, refer to the following...

Three Tactics to Try:

A. Start here: If you're Missing Photos or Videos in the Photos app - Apple Support

B. Check iCloud, Directly:

For Photos: Go here, and see if they reside in iCloud: https://www.icloud.com/photos

C. Where Else to Check:

1. PC
2. PDA
3. eMail
4. Mac Device
5. Cloud Storage
6. Android Phone
7. USB Flash Drive
8. External Hard drive
9. Secure Digital Card
10. Compact Flash Card

You’re not speaking to Apple or Apple employees. We’re all users just like you. This isn’t much of a research project asking for people’s opinions and having no means of verification or authentication. If you’re doing research, contact Apple Corporate.

Corporate Address

Apple

One Apple Park Way

Cupertino, CA 95014

(408) 996–1010

Swing and a miss.