How to Prove a Digital File Existed at a Specific Time
Practical steps to document that a digital file existed in a particular form at a particular time using hashing and timestamps.
Published 2026-08-12 · Updated 2026-09-15 · ProofIt Editorial
Direct answer
Compute a cryptographic hash of the exact file, obtain an independent time attestation for that hash (a trusted timestamp and/or a blockchain record), and keep the resulting certificate and any TSA token so others can verify the claim later without needing to trust you.
Definitions
Existence evidence shows that a specific bit-for-bit file (represented by its hash) was known to exist at a given time. Integrity evidence shows that the file you're presenting now still matches that original hash—so nothing was altered after the fact. Neither is the same as ownership evidence, which is a separate legal question about who holds rights to the work.
Step-by-step process
First, finalize the exact version of the file you want to timestamp—hashing is sensitive to every byte, so re-saving or re-exporting the file afterward will produce a different hash and break the link to your evidence. Second, generate the hash and submit it for timestamping (via ProofIt or an equivalent tool). Third, retain three things indefinitely: the original file itself, the certificate, and any independently verifiable token (such as an RFC 3161 response) that isn't solely dependent on one company staying in business.
Common mistakes
The most common mistake is timestamping the wrong version—for example, hashing a draft and then continuing to edit the file, so the version you'd actually need to defend later no longer matches the recorded hash. Another is relying only on a screenshot of a timestamp rather than keeping the underlying certificate and token, which are what an independent party actually needs to verify the claim. A third is assuming a timestamp alone settles a dispute—it establishes existence and integrity, but ownership arguments typically need additional context (contracts, prior drafts, communications) alongside it.
Where ProofIt fits
Upload or certify a file in ProofIt to generate its SHA-256 hash, an optional RFC 3161 timestamp, blockchain registration, and a certificate with a public verification page. See a privacy-safe example at proofit.biz/sample-certificate, and try the verification flow directly at proofit.biz/verify—no account is required to confirm a certificate's authenticity.
Where it does not fit
This process proves existence, time, and integrity of a specific digital fingerprint—not legal ownership, and not that you are the original creator if someone else can show an earlier timestamp. If ownership itself is contested, see does a timestamp prove ownership for how that question is actually resolved.