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1Warning
2=======
3Mat only removes metadata from your files, it does not anonymise their
4content, nor can it handle watermarking, steganography, or any too custom
5metadata field/system.
6
7If you really want to be anonymous format that does not contain any
8metadata, or better : use plain-text.
9
10Implementation notes
11======================
12Symlink attacks
13---------------
14MAT output predictable filenames (like yourfile.jpg.bak).
15This may lead to symlink attack. Please check if you OS prevent
16against them
17
18Test suite
19----------
20Formats that are not in the test suite are not well-tested,
21please do not trust the MAT about them!
22
23Threat Model
24============
25The Metadata Anonymisation Toolkit adversary has a number
26of goals, capabilities, and counter-attack types that can be
27used to guide us towards a set of requirements for the MAT.
28
29Adversary
30------------
31
32* Goals:
33
34 - Identifying the source of the document, since a document
35 always has one. Who/where/when/how was a picture
36 taken, where was the document leaked from and by
37 whom, ...
38
39 - Identify the author; in some cases documents may be
40 anonymously authored or created. In these cases,
41 identifying the author is the goal.
42
43 - Identify the equipment/software used. If the attacker fails
44 to directly identify the author and/or source, his next
45 goal is to determine the source of the equipment used
46 to produce, copy, and transmit the document. This can
47 include the model of camera used to take a photo, or
48 which software was used to produce an office document.
49
50
51* Adversary Capabilities - Positioning
52 - The adversary created the document specifically for this
53 user. This is the strongest position for the adversary to
54 have. In this case, the adversary is capable of inserting
55 arbitrary, custom watermarks specifically for tracking
56 the user. In general, MAT cannot defend against this
57 adversary, but we list it for completeness.
58
59 - The adversary created the document for a group of users.
60 In this case, the adversary knows that they attempted to
61 limit distribution to a specific group of users. They may
62 or may not have watermarked the document for these
63 users, but they certainly know the format used.
64
65 - The adversary did not create the document, the weakest
66 position for the adversary to have. The file format is (most of the time)
67 standard, nothing custom is added: MAT
68 should be able to remove all meta-information from the
69 file.
70
71Requirements
72---------------
73
74* Processing
75 - The MAT *should* avoid interactions with information.
76 Its goal is to remove metadata, and the user is solely
77 responsible for the information of the file.
78
79 - The MAT *must* warn when encountering an unknown
80 format. For example, in a zipfile, if MAT encounters an
81 unknown format, it should warn the user, and ask if the
82 file should be added to the anonymised archive that is
83 produced.
84
85 - The MAT *must* not add metadata, since its purpose is to
86 anonymise files: every added items of metadata decreases
87 anonymity.
88
89 - The MAT *must* handle unknown/hidden metadata fields,
90 like proprietary extensions of open formats.