Glossary
JUMBF
JUMBF is a generic box format for embedding structured data in a file, and the wrapper every C2PA manifest is stored in.
Updated
Also written: JPEG Universal Metadata Box Format, ISO/IEC 19566-5.
JUMBF — the JPEG Universal Metadata Box Format, standardised as ISO/IEC 19566-5 — nests labelled boxes of data using the same box model as the ISO base media format. On its own it says nothing about images; it is a container for whatever a standard chooses to put in it.
C2PA chose it. A content credential is a JUMBF superbox holding the manifest store, its assertions and the signature. In a JPEG that superbox is carried in one or more APP11 marker segments; in PNG it sits in a caBX chunk; in HEIC and AVIF it is a jumb box.
Removing the JUMBF block is how a C2PA manifest is removed. Because it sits beside the compressed image data rather than inside it, dropping it touches no pixels — and because generic EXIF tools do not look for it, they can report a file clean while the credential is still there.
Related terms
- C2PA — C2PA is a provenance standard that attaches a signed, tamper-evident manifest to a file, describing its origin and edit history.
- APP marker segment — An APP marker segment is a labelled block in a JPEG file where applications store metadata, ahead of the compressed image data.
- ISO BMFF box — A box, sometimes called an atom, is the nested container unit that HEIC, MP4 and MOV files are built from.