How does end-to-end encrypted photo storage work in York Vault?

What end-to-end means in York Vault

The two ends are your own devices. York Vault encrypts each item on the phone that adds it. The item stays encrypted on the disk, in your backup, in York Cloud and on the way between devices. It opens only on a device that holds your keys.

This matters for backups. Apple says that with standard data protection, it keeps iCloud encryption keys in Apple data centers. York Vault does not rely on that. Items reach your iCloud or your Google Drive app data folder already encrypted. The keys stay on your devices. See encrypted backup.

How does York Vault encrypt each item?

• Each photo, video and file gets its own random 256-bit key.
• AES-256-GCM seals the content in 1 MiB chunks. Each chunk has its own nonce.
• Each chunk carries its chunk number and file id as authenticated data. If someone swaps, reorders or cuts chunks, the check fails.
• York Vault also encrypts file names, dates, places, thumbnails and the library index.
• Test vectors and a fuzz test run on every build.

The design and the cipher are the same on iPhone, iPad and Android. That is why a library can move from an iPhone to an Android phone, and back.

How does your code open the keys?

Each library has one random master key. York Vault never stores it in readable form. It stores the master key in wrapped form, in key slots. Each slot has its own salt.

Slot	What opens it	Where a guess can happen
Code	Argon2id of your code (64 MB, 3 passes), plus a key agreement in the chip	Only on your phone
Face or fingerprint	A key in the security chip	Only on your phone
Recovery key	The 12 words from setup	Any device with your backup

A copy of the app files on another device cannot test a single guess. The security chip on your phone takes part in every opening. Wrong-code waits apply to every guess. A change of code rewraps one slot in under 1 second. With iCloud Keychain on, your code also opens your backup on a new iPhone. Without it, your recovery key does.

What does the security chip add?

On iPhone and iPad, the chip is the Secure Enclave. Apple describes it as a separate subsystem, apart from the main processor. Apple says it keeps sensitive data safe “even when the Application Processor kernel becomes compromised.”

On Android, the chip is Android Keystore, in StrongBox where the phone has it. Android Developers says “Key material never enters the application process.” For fast opening on Android, York Vault accepts only Class 3 biometrics. Android rules let no weaker class release keys from Keystore.

On iPhone, the Face ID slot stops working if someone adds a new face or fingerprint in iOS Settings. York Vault then asks for your code. See lock options.

What happens on the phone itself?

When the phone locks. On iPhone, library files use the Complete protection class. Apple says the system discards that key “shortly after the user locks a device”. The files stay sealed until the next time you open the phone.

When York Vault locks. York Vault clears keys and decrypted pictures from memory. Thumbnails exist in decrypted form only in memory. Large files decrypt as a stream, never as a full plain copy.

When you type a code. Code fields use secure entry and turn off autocorrect, predictions and dictation. On iPhone, York Vault refuses custom keyboards, so only the system keyboard can type a code.

When you copy an item. The copy stays on this device and is not sent to your other Apple devices. It clears from the clipboard after 60 seconds. After you paste an item in, York Vault offers to clear the clipboard.

On the network. On iPhone, App Transport Security stays on with no exceptions. Apple says ATS blocks connections below a minimum security level. The share server uses TLS 1.3, and the app checks its certificate.

On a modified phone. York Vault looks for signs of a jailbreak on iPhone, or root on Android. If it finds them, it shows a warning once. It never blocks your items.

Can someone still get in?

The design moves the weak point to your code and your phone. York Vault cannot protect you from these:

• A person who knows your code or sees you type it.
• A phone that malware already controls.
• Copies you export or share. They leave the protection of York Vault, and the app says so before your first export.

To make a guess harder, choose a long code in lock options. For a full review of vault app safety, read are photo vault apps safe.

Can I check the design?

We publish a white paper that matches the code. We also publish an outside audit of the encryption core, and the source code of that core library. The full design is on our security page. To learn what we can and cannot see, read zero knowledge.