Checksum Tool

A checksum is like a code of quality assurance verifying that a file is what you think it is. It often looks something like 5a828ca5302b19ae8c7a66149f3e1e98. However, one checksum of a file is useless without a second checksum of the same file to employ in comparison. When two checksums from the same digital object differ, there might be a fault in the content of the file.

To produce a standard form of checksum, a software tool (screenshot above) scans a digital file at a specific point in time and represents the file content as combinations of numbers and/or letters. The tool calculates the checksum by treating the file content like a string of bits. An algorithm applied to these bits yields a specific “number” like the one in the paragraph above.

Re-run this calculation at a later point in time, and if the result is different—if we get 5a828ca5302b19ae8c7a66149f3e1e10 instead of 5a828ca5302b19ae8c7a66149f3e1e98 —that change in the checksum signals that the file has also changed in some way. The file may be corrupted, missing one of its parts, or it may have been altered legitimately. Hopefully, the checksum remains the same and verifies that you have exactly the same file you did after the first computation of the checksum.

Metadata Extraction Tool

Metadata is crucial to digital preservation. Without information about the digital object saved specifically as a form of metadata, it could be difficult to know many things: the creator of the content, the time it was created, its name or title, focal or aperture information for pictures (among many other image specifications), technical settings and standards for digital sound and video (bit rate, codec, frame rate, etc.), reformatting specifications … the list goes on.

For example, without a label, a tin of canned food holds only mystery ingredients until you open it, thereby ruining the intended preservation of the peaches inside. The label is metadata. So when metadata is not already known, we must pull it out of the file itself via algorithm and save it. Almost every type of file can be plumbed for information, but we need special tools to do it.

A metadata extraction tool is software that analyzes a given file and relays certain characteristics about the file and its content back to you. Usually the tool reveals this information in pre-set, standard ways of displaying metadata. It may also produce a simple table of information, as shown in the MediaInfo example above. Here, we see a list of technical metadata that the MediaInfo tool has collected after performing an analysis of an audiovisual object.