LegalRecorder What is LegalRecorder?

Verify a recording

Check that a recording made with LegalRecorder hasn't been changed, that it came from the phone it claims to, and when it provably existed.

Drop the evidence pack here The .zip shared from the app, or its unzipped folder. Drop two people's packs together to check whether their phones were near each other.
Everything is checked here in your browser. The recording is never uploaded. Only its fingerprint (a SHA-256 hash) is looked up in the LegalRecorder log.

Look up a fingerprint

Already have a SHA-256 hash, or a single file? See whether and when it was registered in the LegalRecorder log, with the log's own independent timestamp.

How the proof works
  1. The app records in short pieces. Each piece's SHA-256 is linked to the previous one in a hash chain, so no piece can be changed, removed or reordered without breaking every link after it.
  2. Each link is signed by a key held in the phone's security hardware. Google's key attestation shows the key was made by LegalRecorder on that phone and can't be copied off it.
  3. Every few minutes, and whenever a recording is kept, the latest link is sent to an independent timestamp authority (Sectigo or DigiCert), which signs the time it saw it. That proves the audio existed by then.
  4. The same fingerprints go to the LegalRecorder log, which batches them every 10 minutes and has each batch timestamped too, so the log itself can't be backdated.
  5. If enabled, the phone also records where it was (GPS and network fixes, mobile cells, Wi-Fi networks) and what was around it (Bluetooth devices), sealed into the same links as the audio. The person sharing can withhold any of it; withheld parts still verify and can be revealed later.
  6. Phones running LegalRecorder can broadcast a random, changing witness code. Each logs the codes it hears, and each keeps the secret behind its own, so two people's packs together show their phones were within Bluetooth range.
  7. The recording's electrical hum can be traced and matched to a grid operator's frequency log, which shows when it was made and whether it was cut.

To check without this site, run tools/verify.py from the LegalRecorder source with Python and OpenSSL. It makes the same checks offline.