Message Digest and Hash
If files, logs, and other information are going to be captured and used for evidence, you need to ensure that the data isn’t modified. In most cases, a tool that implements a hashing algorithm to create message digests is used.
A hashing algorithm performs a function similar to the familiar parity bits, checksum, or cyclical redundancy check (CRC). It applies mathematical operations to a data stream (or file) to calculate some number that is unique based on the information contained in the data stream (or file). If a subsequent hash created on the same data stream results in a different hash value, it usually means that the data stream was changed.
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