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FLAC content provenance

Content provenanceContent provenance: The record of where a piece of content came from and how it changed, carried with the content itself. for FLAC files is a signed C2PA manifestC2PA manifest: The signed label itself: a small package inside a file that records who signed it, what they declared and how to check it. inside the file. Anyone can check who signed it and whether it changed, for free.

Start signing freeCheck a FLAC file
A file holds a signed label in four layers: who signed it, what they declared including AI use, a fingerprint of the content, and a signature that seals them together.
The label sits inside the file. It names the signer, carries what they declared, fingerprints the content, and is sealed by a signature.
File
.flac, MIME typeMIME type: The standard name for a file format, such as image/jpeg or audio/wav, that software uses to decide how to read a file. audio/flac
Where the label sits
Inside the file, in a tag block at the start of the file, as in an MP3.
Standard
C2PAC2PA: The Coalition for Content Provenance and Authenticity: the group that publishes the open standard for content labels., the open standard for content labels.
Made for
Lossless music, Audio archives, Hi-fi streaming, Studio masters

What Encypher supports for FLAC

  • SignSupported

    Encypher signs FLAC files under C2PA 2.2 and 2.4.

  • CheckSupported

    Free in the browser checker, with no account.

  • Formal conformanceNot yet

    Not in our formal conformance record. That record is a narrower test than signing and checking.

How to check a FLAC file

  1. Open the free checker.

    It runs in your browser. No account needed.

    Open the checker

  2. Add your FLAC file.

    Drop it in or pick it from your device.

  3. Read the result.

    It shows who signed and what they declared, such as AI use. It also shows if the file changed.

Where the label sits in a FLAC file

The file starts with an ID3 tagID3: The tag block in an MP3 file that holds its title, artist and other details., a block of details like title and artist. The label is one frame in it.

In an MP3 or FLAC file, the label is one frame in the tag block at the front of the file, ahead of the sound.
A FLAC file keeps the label in a tag block at the start of the file, as in an MP3.

FLAC is lossless compressed audio. It keeps the full sound at about half the size of WAV, so archives and hi-fi stores use it.

What keeps the label on a FLAC file

You can add a hidden watermarkWatermark: A mark placed in the content itself, visible or hidden, so it can be found again after the file is copied. when you sign. If a copy loses its label, the watermark can lead back to the record.

Hard binding is a fingerprint of the exact file, so a re-encode breaks it. Soft binding is a watermark in the picture that still leads back to the label after a re-encode.
The fingerprint proves the file is unchanged. The watermark finds the label again when the file has changed or lost it.
  • Copying and moving the file keep the label.
  • Editing the sound after signing shows as a change.
  • Converting to another format writes a new file without the label, so sign the copy you publish.

For engineers

Show the technical detail
Embedding
JUMBF manifest store in a leading ID3v2 GEOB frame (MIME application/c2pa); legacy FLAC APPLICATION blocks (app id c2pa) remain readable
Accepted MIME types
audio/flac
Signing versions
C2PA 2.2, 2.4
Verification
Any version. The checker reads any C2PA manifest it can parse, and the report names the version it checked against.
curl -X POST https://api.encypher.com/api/v1/sign/media \
  -H "Authorization: Bearer $ENCYPHER_API_KEY" \
  -H "Idempotency-Key: $(uuidgen)" \
  -F "file=@example.flac" \
  -F "title=My FLAC file" \
  -F "action=c2pa.created"

Support rows come from the live API capability matrix. Full reference: C2PA media types.

Keep reading

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