Apple's SensitiveContentAnalysis framework delivers 99%+ accuracy with less than 1% false positives. Beach photos and medical images won't be flagged.
Never. All analysis happens on your device using Apple's Neural Engine. Zero network requests, zero cloud uploads.
ChaCha20-Poly1305 encryption with 256-bit keys stored in the iOS Secure Enclave. The vault is protected by FaceID/TouchID.