86 lines
3.0 KiB
Markdown
86 lines
3.0 KiB
Markdown
Threat Model
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The Metadata Anonymisation Toolkit 2 adversary has a number
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of goals, capabilities, and counter-attack types that can be
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used to guide us towards a set of requirements for the MAT2.
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This is an overhaul of MAT's (the first iteration of the software) one.
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Warnings
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--------
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Mat only removes standard metadata from your files, it does _not_:
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- anonymise their content
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- handle watermarking
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- handle steganography
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- handle any non-standard metadata field/system
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If you really want to be anonymous format that does not contain any
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metadata, or better : use plain-text. And as usual, think before clicking.
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Adversary
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------------
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* Goals:
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- Identifying the source of the document, since a document
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always has one. Who/where/when/how was a picture
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taken, where was the document leaked from and by
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whom, ...
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- Identify the author; in some cases documents may be
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anonymously authored or created. In these cases,
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identifying the author is the goal.
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- Identify the equipment/software used. If the attacker fails
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to directly identify the author and/or source, his next
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goal is to determine the source of the equipment used
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to produce, copy, and transmit the document. This can
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include the model of camera used to take a photo, or
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which software was used to produce an office document.
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* Adversary Capabilities - Positioning
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- The adversary created the document specifically for this
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user. This is the strongest position for the adversary to
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have. In this case, the adversary is capable of inserting
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arbitrary, custom watermarks specifically for tracking
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the user. In general, MAT cannot defend against this
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adversary, but we list it for completeness.
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- The adversary created the document for a group of users.
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In this case, the adversary knows that they attempted to
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limit distribution to a specific group of users. They may
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or may not have watermarked the document for these
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users, but they certainly know the format used.
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- The adversary did not create the document, the weakest
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position for the adversary to have. The file format is (most of the time)
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standard, nothing custom is added: MAT
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should be able to remove all meta-information from the
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file.
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Requirements
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---------------
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* Processing
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- The MAT2 *should* avoid interactions with information.
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Its goal is to remove metadata, and the user is solely
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responsible for the information of the file.
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- The MAT2 *must* warn when encountering an unknown
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format. For example, in a zipfile, if MAT encounters an
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unknown format, it should warn the user, and ask if the
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file should be added to the anonymised archive that is
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produced.
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- The MAT2 *must* not add metadata, since its purpose is to
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anonymise files: every added items of metadata decreases
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anonymity.
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- The MAT2 *should* handle unknown/hidden metadata fields,
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like proprietary extensions of open formats.
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