Security Stripes: Visible Seals for Robust Documentation and Authentication of Digital Images
Charles Bradley* and James Mancuso Advanced Microscopy Techniques, 3 Electronics Ave., Danvers, MA 01923
*
cbradley@amtimaging.com
Introduction Digital images carry a great deal of information, but
they should not stand alone. Tey need to be accompanied by experimental variables, equipment used, personnel involved, image-processing operations performed, and site information. It is essential to maintain a link between pixel data and experi- mental conditions associated with the picture. Concern for the integrity of digital images presented in
scientific studies has been growing in prominence [1, 2, 3, 4, 5]. Although manipulation of digital images is generally not malevolent, its relative ease exacerbates ethical and security issues that are less prevalent with film-based recording, where the common practice of pasting a print into a lab book and recording an exposure number creates a visible and permanent record. Permanence is important not only for maintaining organized, traceable, and intelligible records but also for supporting the authentication requirements of industry, medicine, and research funding. We describe here the concept of a security stripe as a robust
seal for recorded images. Like a product bar code, it is immedi- ately visible and it contains information about the carrier. It can also authenticate the data collection process. Te security stripe is compatible with all loss-less recording formats. So it can be widely adopted without compromising legacy files or obsolescing preexisting proprietary formats and the soſtware that is dependent on those formats. In addition the security stripe can encode text in Unicode thereby permitting use of native character sets.
Current Image Recording Practices A simple and common way of documenting an image is
to create a companion file, which records instrument settings and experimental conditions. Tis can be in a notebook, although some instrument makers [6] create with each image a companion digital file containing this type of information. Tese digital files can be comprehensive, but they are vulnerable to being separated from the original or lost. Companion data can also be saved in a database, but this impedes information exchange as all collaborators and examiners of the image then need access to the database soſtware and the database files. More importantly, neither companion files nor databases address validation as they are separate from their respective images. Another approach to documentation is to include metadata
containing the equivalent to a companion file within a propri- etary image format [7]. Similar metadata can authenticate the image by the use of security keys or image self-consistency measures. Te main drawback of proprietary formats is that they impede easy exchange of original data. When propri- etary files are exported to a standard format, such as TIFF, the companion metadata and security metadata are oſten lost.
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Figure 1: Possible fates of TIFF tags. Information stored in a tag in a TIFF header can be used properly or improperly, or it can be silently stripped from the file. Because tags are not visible, this silent stripping of image data may go unnoticed for long periods.
doi:10.1017/S1551929510000866
www.microscopy-today.com • 2010 September Standard format images can also embed experiment
and authentication data within more standardized metadata structures such as TIFF tags (see Figure 1). Unfortunately, this approach is limited to a specific image file format. Even within a single protocol such as TIFF there can be serious problems in placing companion information into a tag. First, the TIFF standard requires reading programs to ignore tags that they do not use, which effectively strips them from the file when the image is re-saved. Second, most tags do not have a rigorous definition, and there is no provision for collisions where two applications interpret a given tag differently. Te weakness of this approach is illustrated when saving
microscope companion data in the Image Description tag, one of Abode’s standard TIFF tags. Te tag is defined in the Adobe TIFF 6 Standard as “A string that describes the subject of the image. . . . For example, a user may wish to attach a comment such as ‘1988 company picnic’ to an image.”[8] Tis is a very flexible specification, which can be, and has been, implemented differently by different programs. For example, ImageJ and Microsoſt Paint write their version into this tag. Te Open Microscopy Environment [9] has another recommended format for this tag for microscope data. However, in practice, it is used inconsistently by both camera suppliers and microscope vendors. Tus even loss-less saving in TIFF does not ensure preservation of companion data.
Authentication and Validation Because concern for the integrity of digital images presented
in scientific studies has been growing, government funding agencies and many journals are now adopting techniques from the rapidly emerging field of image forensics to detect image manipulation [10, 11, 12, 13, 14]. Several journals [3, 4, 5, 15]
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