How the opposing party can verify digital evidence
The real strength of digital evidence is not that you declare it genuine. It is that anyone — including someone hostile to you — can verify it independently, without trusting you. This is the exact opposite of how most digital evidence works.
The "trust" problem
Much digital evidence ultimately asks you to trust whoever presents it. In court that is precisely the other side's foothold: "who says the file is genuine and was not altered?". If the answer is "trust us", the evidence is already in trouble.
Independent verification flips the burden
A C.E.R.T.O. bundle verifies itself. Along with the evidence you hand over the tools to check it: the BagIt bundle contains a verification script (verify.sh for Mac/Linux, verify.bat for Windows) and the certificates it needs (tsa-ca.pem). Anyone can run it on their own computer, without owning C.E.R.T.O.
On Mac and Linux, open the Terminal, move into the bundle folder and type sh verify.sh; on Windows, double-click verify.bat. Recomputing the hashes works offline too. The signature and the timestamps need OpenSSL 3: if it is missing on a Mac, the script downloads a small verification kit once and checks its hash before using it; on Windows the instructions are in the README.txt file. Last, the script asks our register whether the exhibit is on record: an optional step that can be switched off.
What the verification checks
- the battery of hashes: it recomputes each file's fingerprints and compares them with the sealed ones — if even one bit changed, it shows;
- the double RFC 3161 timestamp: it confirms the capture date (inner anchor) and the sealing date (outer seal) are genuine and certified by a third party;
- the Ed25519 signature: it confirms the bundle was created by that specific device and was not reworked;
- the integrity of the CASE/UCO description: the file that records the chain of custody is hashed too, and any change to it would be detected.
At the end, the verification returns a clear result: "BUNDLE VALID" or not valid. If the tool needed for a check is missing, the script reports that check as not performed: it passes it off neither as successful nor as failed.
Why it changes everything in court
The other side's technical expert does not have to believe your bundle: they re-check it, and either confirm it is genuine or find the tampering. And because the formats are open and standard (BagIt, CASE/UCO, RFC 3161), there is no proprietary black box to attack. The discussion moves from “trust us” to what can be checked.
This is why well-captured evidence is harder to challenge on technical grounds: it does not ask for trust, it offers verification. How much weight it carries remains for the court to assess. Read more on the chain of custody and why a screenshot alone is not enough.