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Posts tagged 'digital signatures'

An introduction to the PRONOM contribution model and the Signature Developer role

My name is David Clipsham and I have been employed as the File Format Signature Developer for a month, having previously worked as Customer Service Manager for the cross-government social collaboration tool, Civil Pages. My role is to improve the coverage of The National Archives’ PRONOM file format registry. The internal and external signature information contained in the PRONOM registry is utilised by our file format identification tool DROID, which is used to identify file formats so we can make informed decisions about the long term preservation of digital records.

The PRONOM contribution model

My day is typically spent researching obscure and not-so-obscure file formats, picking through the internal code of each format and identifying the key characteristics that make the file format what it is, as described in Ross Spencer’s recent blog post. I then recreate the key byte sequences, test them against sample files and upload them to PRONOM, ready for our bi-monthly signature release.

How do I focus my research?

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CAFED00Ds and CAFEBABEs

Wouldn’t it be cool if every digital file created could be identified with a signature or ‘magic number’ of some kind? This would make preservation, and the concept of knowing what you’ve got in order to be able to preserve it, that much easier.

By design or otherwise, for some file formats this is actually the case. The title of today’s blog post provides two such magic numbers used to identify Java class objects and Java pack200 files. These aren’t the first examples to use magic numbers but 0xCAFEBABE is the one I find the most striking as an introduction to the concept. You can read more on the origins of 0xCAFEBABE at Wikipedia. Continue reading »