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 · ProofIt Editorial
Direct answer
Compute a cryptographic hash of the exact file, obtain an independent time attestation for that hash (trusted timestamp and/or blockchain record), and keep the certificate and any TSA token so others can verify later.
Definitions
Existence evidence shows a specific bit pattern was known at a time. Integrity evidence shows the file still matches that hash. Neither equals ownership.
Where ProofIt fits
Upload or certify a file in ProofIt to generate hashes, optional RFC 3161 timestamps, blockchain registration, and a verifiable certificate with a public verify flow.
Demonstration
See a privacy-safe sample certificate and verification steps at https://proofit.biz/sample-certificate and https://proofit.biz/verify.