![]() ![]() In such a system, any modification to the image without re-signing the metadata would be a sign of tampering (provided the signed metadata is still readable within legacy tools). It wouldn't be impossible to remove this metadata, but it would be difficult, if not impossible, to forge such a signature. Of course, so long as any application exists that can open a given file format and then resave it as another where metadata and image permanence are no longer guaranteed, it's a moot point.Īs one alternative, some have suggested the idea of integrating signed metadata into images. As a result, insisting on permanent metadata would likely eliminate many legacy and open source (or small developer) tools from being used in an image workflow where metadata permanence is involved. The applications, file formats, and workflows, which we currently use today are simply not designed for the more rigorous practices that will be needed to assure metadata and image permanence. ![]() ptif for a protected TIFF) which would also break backwards compatibility. At minimum, guaranteeing permanence in metadata would require new extensions to existing file formats(like. ![]() The reality is that in order to protect metadata this way will require major architectural changes throughout ALL image editing, metadata annotation, and image database tools. Major Architectural Changes Will be Needed Take a look at how long it has taken to get XMP support up to the level it is today (and that system still has a number of limitations) then add an additional component-like permanence-and you raise a number of conflicting requirements, making it exponentially harder to carry out. Unfortunately, today, unprotected data containers such as EXIF, IPTC/IIM, or XMP are inherently modifiable, and it will take a significantly more complex system to change that, and that can’t happen overnight. I fully understand why photographers and image owners want their metadata to be permanent-they want it to be unalterable and perpetually associated with the image, regardless of the workflow through which it may travel. Whenever someone performs a screen grab (or a series of them for a larger image), extracts a TIFF file from an Adobe Acrobat (PDF) file, or even copies and pastes the pixel data from one image frame to a new one, the original metadata is left behind as the current systems don’t tie the metadata to the pixel stream for these operations. The metadata for most file formats is stored within a portion of the file header, and it can be difficult to prevent access to that data without also causing restrictions on what can be done with the pixel data. Part of this reason is that at a digital level, a digital image is just a large blob (binary large object) of bits, which when compared to other file formats-with the exception of digital video files-can be quite large. Pixels and Metadata are Part of the same BLOBĪt present there is no definitive answer, and probably will not be for some time to come. The “file header” is the non-image portion of a digital image file, preceding or following the actual pixel data, which contains a marker segment or other information about the file such as those contained in various types of technical, descriptive and administrative metadata typically written using the EXIF, IPTC or XMP standards.ĭespite the specifications in the latest IPTC (International Press Telecommunications Council) schema requesting that the Creator and Source fields be considered as write-once fields, few developers (with the exception of HindSight’s METAmachine) have implemented this request. To clarify, when we are talking about embedded photo metadata I’m referring to the chunk of IPTC-IIM or XMP metadata that has been inserted into the header of the image file. According to John Nack of Adobe, this has been a perennial request from photographers for many years. This idea of permanent metadata is not a new one. When presenting around the country during the GetMETAsmart tour, one question that nearly always came up, was how to lockyour photo metadata so that it could not be changed by others. ![]()
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