Apple has implemented an innovative privacy-preserving search feature in iOS 18's Photos app using homomorphic encryption technology. This advancement allows users to search their photo libraries with enhanced accuracy while maintaining data privacy.
The new system, codenamed "Wally," enables the Photos app to identify specific objects and scenes in images without sending actual photo data to Apple's servers. Instead, it uses encrypted numerical representations called embedding vectors that describe image contents mathematically.
When a user searches for something like "golden retriever," the app encrypts the search query using homomorphic encryption before sending it to Apple's servers. This special type of encryption allows Apple to process the encrypted data and return relevant matches without ever seeing the original query or understanding what the user was searching for.
The technology works by performing mathematical operations on encrypted values:
- The user's device encrypts the search query
- Apple's servers process the encrypted data without decrypting it
- The servers return encrypted results
- Only the user's device can decrypt and display the final results
To balance privacy and performance, Apple employs "somewhat homomorphic encryption" rather than full homomorphic encryption, as the latter would be too computationally intensive for real-world use. The system also uses differential privacy techniques and an anonymization network to further protect user privacy.
While this represents a major step forward for privacy-preserving cloud computing, some security researchers have raised questions about the implementation details and whether users should have been given clearer opt-in choices for the feature.
The introduction of homomorphic encryption in iOS 18 demonstrates Apple's continued focus on privacy-preserving technologies, allowing cloud services to process user data without actually accessing its contents. This could pave the way for more privacy-focused features across Apple's ecosystem in the future.