How can I create independently verifiable evidence of confidential work without making it public?

Timestamp a fingerprint while keeping the work private

A cryptographic hash is a digital fingerprint calculated from a file’s contents. It lets someone check whether a file matches a previously recorded fingerprint. A secure hash function is designed to make reconstructing the contents from the fingerprint computationally infeasible, as described by NIST.

A timestamp service can work with that fingerprint instead of the file. For example, RFC 3161 specifies that a timestamp authority processes a hash representation of the data. The resulting token can later be checked against the file without the authority having received its contents.

The hash alone does not establish a date. It needs a verifiable link to the timestamp or other dated record.

Check what leaves your device

Calculating a file’s hash is a straightforward operation that can be performed locally on your computer. There is no need to upload the file to calculate its fingerprint. For timestamping, that fingerprint can be sent to the provider while the file stays on your device.

Check that this is how the service actually works: is the hash calculated locally, or is the file uploaded and hashed on the provider’s server? If the service also stores your files, check whether they are encrypted before upload and who can obtain the decryption keys. The important question is what reaches the server: only a fingerprint, encrypted files, or readable contents.

Also check whether filenames, descriptions or other metadata become visible. A confidential project title can reveal information even when its files remain unreadable.

Keep enough material to verify the record independently

Preserve the exact certified files, their certificates, the supporting verification data and instructions for checking them. If the files are encrypted, retain a secure way to recover the keys as well. A certificate cannot reconstruct a missing file, restore an altered file to its certified version or unlock one whose key is lost.

Test the verification process while the material is available. A reviewer should be able to establish both that the file matches the recorded fingerprint and that the dated evidence is valid. For an RFC 3161 token, this includes checking the timestamp authority’s signature and the relevant certificate information, as set out in section 2.2 of the standard.

Ask whether the checks can be performed with exported material and independent tools, rather than only through your account on the original provider’s website.

Decide who may examine the files later

Independent verification does not mean anyone can read the work. To check that a particular document matches its certificate, a reviewer needs access to that document, whether through a controlled review or a private copy. They do not need you to publish it for everyone.

For example, you could timestamp an unpublished process description now, keep it confidential, and later provide the exact file and verification material to an authorised expert. The expert could check the dated record without making the description public.

Plan that access separately: identify the recipient, the permitted purpose and any confidentiality terms. WIPO’s trade-secret management guidance describes access controls and contractual measures as parts of protecting confidential information. Timestamping supplements those measures; it does not establish ownership or prove that the information has remained secret.