How to prove you did not use AI to write something

You cannot prove that you did not use AI. You can show how you wrote something, in enough detail that the honest explanation is the likely one: notes and drafts with dates, a revision history, and best of all a record kept while you wrote, every pause, deletion and paste in order, timestamped by an independent authority. OBSCURA Authorship keeps that record on your own device, and anyone you give it to checks it free at /verify-authorship.

Why a detector’s score is not evidence

An AI detector reads a finished text and gives a probability. It does not know how the text was made; it guesses from patterns in the words, and the guesses are wrong often enough to matter. OpenAI withdrew its own AI text classifier in July 2023 because it was not accurate enough. A study published in Patterns in 2023 found that seven detectors, on average, labelled more than half of a set of essays by non-native English speakers as written by AI, when people had written all of them. Plain, careful writing, the kind a student is taught to produce, is exactly what such tools find suspicious.

So the useful question is not “what does the detector say?” but “what does the record of the writing show?”

What counts as evidence of how you wrote

• A record of the process, kept as you wrote. Every run of typing, every deletion and every paste, with its time, in a form that cannot be edited afterwards without it showing. This is the strongest thing you can have, because it shows the work growing, being revised and being left and returned to over real time.
• Independent timestamps. A timestamp from a time-stamping authority (RFC 3161) is a signed statement that a fingerprint of your record existed at a moment. It is what stops a record being written later and back-dated.
• Notes, outlines and earlier drafts, with their file dates and, better, saved somewhere that keeps a history.
• Your sources: the books, articles and pages you used, and where in the text you used them.
• Being able to talk about it. Explaining your argument, why you cut a paragraph, or what you would change is evidence too, and teachers rely on it.

Start before anyone asks

Evidence made afterwards is weak. Write in something that keeps a record from the first word. In Authorship that is the default: start a piece, write, and the record is kept as you go, in the browser on your own device, sealed in blocks that each hold the SHA-256 of the one before. Turn on timestamps in Record and, every ten minutes of work, a 32-byte fingerprint of the record goes to DigiCert’s public authority and comes back signed. Your words never go.

If your teacher issues an assignment brief through Authorship, begin from it: its random code goes into the first block of your record, which shows every keystroke came after the brief existed.

Hand it over

When you finish, Share makes a .oauthor file: the work as Markdown, PDF and Word, the record, the timestamps and a summary PDF with a timeline. Whoever you give it to opens /verify-authorship, free and with no account, and sees each check (the chain, the rebuilt document, the timestamps, your device’s signature) and can replay the writing at any speed. The figures are given as facts, such as how many characters were typed and how many pasted, never as a verdict.

What it cannot do

What no record can do is prove that no AI was involved. Someone could read text from another screen and type it in by hand, and a determined forger could write a program that types for them. A record makes that expensive, because every pause, slip and revision has to be produced in real time and the timestamps fix when each part existed; it does not make it impossible. Anybody who tells you a tool can prove a negative is selling something.