Evidence stacks: a dated record you can check

What an evidence stack is

In an evidence stack, every photo, video, voice memo and document added gets the time, a fingerprint of its exact bytes and, if you choose, where your iPhone was, and each fingerprint covers the one before it.

A fingerprint here is a short code worked out from every byte of a file. Change one pixel and the code changes completely. Because each entry’s fingerprint also covers the entry before it, the entries form a chain. Take one out, swap two, or slip one in later, and the chain no longer adds up.

When a dated record helps

• Damage after a storm or a burst pipe. Keep the photos and the repair quotes together for an insurance claim.
• A dent on a rental car. Photograph it at the counter, before you drive away.
• Work on your home. A contractor’s progress, week by week, with the receipts beside the photos.
• Things you lend or sell. The condition of a car, a camera or a bike on the day it changed hands.

In each case the question later is the same: was this file really taken then, and has it changed since? An evidence stack lets you answer the second part.

What it shows, and what it can’t

An evidence stack is tamper-evident, not a legal guarantee: it shows whether anything changed after it was added, as far as the vault can tell.

That sentence is the honest limit. The stack can show that a file in it is the same file that went in, byte for byte, and that nothing was taken out or reordered. It can’t show what was in front of the camera. It can’t vouch for a photo that was already edited before you added it. And whether an insurer, a court or anyone else accepts the record is their decision, not the app’s.

The report

An evidence stack makes a PDF report with each file’s SHA-256 fingerprint, and explains how to check a file yourself with shasum on a Mac or certutil on Windows.

So the person you share the report with doesn’t have to trust the app. They can take the file you send them, run the check on their own computer, and compare the result with the fingerprint printed in the report. If the two match, the file is the one that went in.

Making one

1. On the Stacks tab, touching and holding the plus button offers New Stack, New Time-Sealed Stack and New Evidence Stack. Choose New Evidence Stack.
2. Turn on Record the place if where your iPhone was matters, then create the stack.
3. Add photos, videos, voice memos or documents as things happen, not all at the end.
4. When you need the report, open the stack. Export Report makes the PDF, and you can choose to include the original files with it.

Adding things as they happen is what gives the times their meaning. A batch added months later only shows when you added it.

Changes after the fact

The chain is built so that changes show, not so that nothing can ever change.

• Edits. Editing a file from an evidence stack makes a new item outside the stack, so what went in stays as it was.
• Removals. Removing a file from an evidence stack adds a removed entry to its chain, so the removal shows too.

Free or Pro

Creating a time-sealed stack or an evidence stack is part of Sealed Pro, while opening one and adding to it are not.

Where Sealed helps, and where it doesn’t

It helps you keep a dated, checkable record of files, in a place where any later change would show. In an evidence stack, every photo, video, voice memo and document added gets the time, a fingerprint of its exact bytes and, if you choose, where your iPhone was, and each fingerprint covers the one before it.

It doesn’t do these things:

• Count as legal proof by itself. An evidence stack is tamper-evident, not a legal guarantee: it shows whether anything changed after it was added, as far as the vault can tell.
• Vouch for a file before it went in. A photo edited before you added it carries that edit, because the chain starts when the file is added. In an evidence stack, every photo, video, voice memo and document added gets the time, a fingerprint of its exact bytes and, if you choose, where your iPhone was, and each fingerprint covers the one before it.
• Come free to create. Creating a time-sealed stack or an evidence stack is part of Sealed Pro, while opening one and adding to it are not.
• Replace advice. For anything that may end up in a dispute, ask the person who will judge it what they need. The documents guide covers keeping the paperwork itself.