Checksum

A checksum is a short fingerprint computed from a file, which changes if even one byte of the file changes.

sha256 is the one most commonly used for evidence. Two files with the same sha256 are the same file; two files with different sha256 values are not, however similar they look.

In practice it does two jobs. It proves a document has not been altered since it entered the file, and it stops the same document being imported twice under two different names.

Legalnaut builds this out of your own case file. See the plans.