Someone hands you a document and later the question is whether it is the same document. PROVENANCE takes a fingerprint of the file the moment it reaches you, along with a note of where it came from, and re-checks it whenever you need to. If a single bit has changed, the fingerprint changes with it.
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Short form
SHA-256
SHA-512
The written record
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Be clear about what this does. It proves a file has not changed between two checks, because SHA-256 changes if any bit does. It does not prove when you had the file: the time in the record comes from the clock on this machine, and a clock can be set to anything, so on its own the date carries no weight against anyone who disputes it. To make the date mean something, publish the digest somewhere you cannot quietly edit later and that keeps its own timestamp: email it to yourself and to someone else, post it publicly, put it in a git commit, or lodge it with a solicitor. It is the third party that gives the date its force, not this page. Renaming a file does not change its digest, and neither does copying it; editing it by one character does. Nothing here is uploaded or stored.
Questions people ask
How do I prove a file has not been altered?
Take a cryptographic hash of it the moment it reaches you and keep that value somewhere safe. Re-hash the file later and compare. SHA-256 changes completely if any bit changes, so an identical digest means an identical file, down to the byte.
Does a hash prove when I had the file?
No, and this is where most home-made custody records fall down. The date in the record comes from the clock of the machine that wrote it, and a clock can be set to anything. To give the date force, publish the digest somewhere you cannot quietly edit later and that keeps its own timestamp: a git commit, an email to a third party, a public post, or a solicitor's file.
Does renaming or copying a file change its hash?
No. The hash is computed over the contents, so renaming, copying or moving leaves it identical. Opening the file in an application and saving it does change it, frequently even when you changed nothing on screen, which is why you hash first and then work on a copy.