Is there any kind of ink, or other substance, that can be used to identify the age of a paper document?
Please do not tell me just to write the date on the page. I do that already, and of course it can be forged. I am looking for something that I can put on the page, so that anyone at a later date can establish the age of the document.
Ok that is about all - Ficer67
There’s no chemical process that will work since it’s going to be so highly dependent on the environment (temperature, humidity, etc.). A radiometric technique could work, but that’s going to be expensive (and also not very reliable).
Tamper-resistant paper exists. It makes the document difficult to forge or alter. Another party could not easily remove the old date and insert a new one. There are also tamper-evident tapes that could be applied over the date.
You could also cryptographically sign the document. No one could alter the document without breaking the signature. The trouble is that there’s not an obvious way to consistently turn a physical printed page into a digital file. You could print out a hex dump of the signed file along with the original document.
Postmark? Notary stamp?
Run it down to your local County Recorder and have it recorded. Your document will be clearly dated and difficult to alter.
delete post
Embossing? Dot matrix time&date printer? Fingerprint over the handwritten date? Wax seal?
Do you need to do this for one document or thousands of them?
Assuming your objective is to establish that a document existed in that exact form no later than a specific date, it can be done electronically by scanning the document and emailing it to a mail service where end users have no ability to tamper with the database or headers (i.e. most webmail services).
For the actual paper hard copy, I can’t think of any solution - simply because anything that, for example, degrades or changes over time*, is only going to do that for a finite period before it is 100% degraded or changed, and won’t change any further - so for example, an ink that changes colour over a 10 year period, then stops, will, at 15 years old, still only look 10 years old.
*There are inks and processes designed to do that for stock rotation etc - although not in practice AFAIK
I think it was a discussion about forged historical documents where someone said that they got period paper by finding really old books in the library and cutting out the blank pages at the front or back of the binding.
The chemical composition of ink can also give a clue - IIRC that’s what was the giveaway for “Hitler’s Diaries”.
On 4 May, 15 volumes of the diaries were removed from the Swiss bank vault and distributed to various forensic scientists: four went to the Bundesarchiv and eleven went to the Swiss specialists in St Gallen. The initial results were ready on 6 May, which confirmed what the forensic experts had been telling the management of Stern for the last week: the diaries were poor forgeries, with modern components and ink that was not in common use in wartime Germany. Measurements had been taken of the evaporation of chloride in the ink which showed the diaries had been written within the previous two years.
But if we’re just talking about a document you’re creating yourself, now, I can’t think of any easy way other than - as others suggest - impartial third party like an email server, notary public, or sealing in an envelope in the lawyer’s office.
Thanks for the great responses guys. I have come to the conclusion that what I want to do is possible, but impractical. Lots of things are like that.
Thanks again
Maybe there is a print driver that lets you do a custom version of this:
That hidden yellow dot technique was intended to trace people using colour xerox to reproduce money.
The point is, I can’t think of a technique that can’t be faked later, other than a reliable third party vouching for the authenticity. It’s like having the kidnap victim hold up today’s newspaper while you take a photo to prove they are still alive today - except reverse. What can you do to prove something was exactly as it was two months ago or two decades ago or two centuries ago, using evidence you only provide today?
Actually, I think it’s kind of possible (there are still flaws here) with asymmetric encryption, but would require the services of a trusted third party. I’m thinking something like:
The print driver requests a date mark from the printer manufacturer; their server encrypts a string containing the date, time, and other stuff, and passes this back to the printer, which prints the encrypted data on the page.
Anyone with the public key can examine the data and verify the date. Only the printer manufacturer can generate encrypted date codes for arbitrary dates.
Of course, that wouldn’t prevent someone taking the date code from an existing document and copying it onto a new one - which would appear to date that document the same - but you would only be able to pick dates from existing printed documents, not choose any arbitrary past date.
That copying could be prevented by including some sort of hash of the document content in the encrypted data - except that hash would need to be able to be reconstructed from the hard copy, not the electronic form of it, and that would have to remain possible even after wear and tear.
I was mowing the grass today and stepped on a branch. Seeing the jagged ends reminded me of split tally sticks. You could encode the date on a tally stick and handwaves permanently bond it to the document. You retain the other spilt which is used to authenticate the document. If you really wanted to be secure, make the tally stick from an antique piece of wood and burn the remains. Use the wood’s DNA to further verify authenticity.
Now that would be a contract with teeth.
I think it’s simple enough to concieve of a date stamp method that is both indelible and unalterable - for example, a punch that stamps the date onto paper by cutting the digits as a fine dot matrix of tiny holes.
Easy enough to design the character set so that no digit can be transformed into any other digit by adding more holes, and once a document is punched, there’s no way to undo it. More than one punched date indicates tampering. A torn off corner with the punch in the wrong place indicates tampering.
The problems are: knowing when the punch was applied and whether the digits were a correct representation of that date.