52 lines
2.0 KiB
Markdown
52 lines
2.0 KiB
Markdown
# Exiftool
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mat2 is in fact using exiftool to extract metadata from files,
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but not to remove them. The previous iteration of mat2, MAT,
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was using exiftool to remove metadata, which lead to several cases where
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they weren't correctly removed, if at all.
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For example, [Exiftool's documentation](https://www.sno.phy.queensu.ca/~phil/exiftool/TagNames/PDF.html)
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states the following with regard to PDF:
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> All metadata edits are reversible. While this would normally be considered an
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advantage, it is a potential security problem because old information is never
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actually deleted from the file.
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To remove metadata, mat2 usually re-render the file completely, eliminating
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all possible original metadata. See the `implementation_notes.md` file for
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details.
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# jpegoptim, optipng, …
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While designed to reduce as much as possible the size of pictures,
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those software can be used to remove metadata. They usually have very good
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support for a single picture format, and can be used in place of mat2 for them.
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# PDF Redact Tools
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[PDF Redact Tools](https://github.com/firstlookmedia/pdf-redact-tools) is
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a software developed by the people from [First Look
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Media](https://firstlook.media/), the entity behind, amongst other things,
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[The Intercept](https://theintercept.com/).
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The tool uses roughly the same approach than mat2 to deal with PDF,
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which is unfortunately the only fileformat that it does support.
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It's interesting to note that it has counter-measures against
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[yellow dots](https://en.wikipedia.org/wiki/Machine_Identification_Code),
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a capacity that mat2 [doesn't possess yet](https://0xacab.org/jvoisin/mat2/issues/43).
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# Exiv2
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[Exiv2](https://www.exiv2.org/) was considered for mat2,
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but it currently [misses a lot of metadata](https://0xacab.org/jvoisin/mat2/issues/85)
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# Others non open source software/online service
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There are a lot of closed-source software and online service claiming to remove
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metadata from your files, but since there is no way to actually verify that
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they're effectively removing them, let alone adding unique markers, they
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shouldn't be used.
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