A creation having acquired a certain date is a creation which has been time-stamped and stored with integrity.

However, proving the integrity of digital proof means proving there have been any alteration since the registration. Thus you can ensure the proof retain its original state all way long its storage since the timestamp. 

 

The so-called "naive" solution for most time stamping services

 

When a service provider receives proof of creation, he keeps a copy of the document with the date, time and identity of the customer. In this way, if the integrity of the file is questioned, the client can compare his copy with that held by the provider. If there are identical, this is supposed to mean that no modification has been made and that the customer was in his possession at least on the days of receipt of the document by the service provider. The majority of providers keep this copy in electronic or paper form in a place they control. This can be on servers or in their office.

The problem with this solution is that it forces the user to trust his provider. Indeed, as early as 1991, Scott Stornetta and Stuart Haber spoke of a naive solution and stressed that apart from having confidence in these providers, there is nothing to prove that they did not modify, during storage, the data stored. Nothing prevents the time stamping service provider from agreeing with his client to change the date of the time stamp to be provided.

 

The solution provided by the blockchain

 

At that time, the solution both of them found was to publish the copy of the time-stamped document in a newspaper with a large circulation which made it impossible for anyone, including themselves to backdate or alter the deposits. This would require being able to retrieve all newspapers copies in circulation and replace them.Thus the proof becomes mathematical.

 

Fortunately, in blockchain, these reproductions are no longer made on a newspaper but on servers. To illustrate this change, let’s compare an event taking place on the blockchain - example - the deposit of a work of art - with an event taking place in the real world - example - a piano fallen from the sky. In this example, the fall of the piano will be much easier to prove if it was seen in the middle of Strasbourg in front of more than a hundred witnesses rather than seen in a campaign by a single resident. This logic is the same for ta timestamp creation. The more servers save the event, the less this event can be disputed.

 

The importance of choosing the blockchain

 

However, the servers on which the creation is replicated must be independent of each other. Indeed, if all servers are controlled by a single and same entity then the problem remains the same, this entity will be able to modify the copy of the proof on the servers that it controls regardless of the number of servers which replicate the proof in question .

Open blockchains, that is, allowing any user to take part in the operation of the network guarantees these users a sufficient level of independence. In these blockchains, the more users there will be, the more robust the evidence will be because it becomes extremely difficult to take control of it.

The best example concern the Ethereum scandal called « THEDAO ». Majority of users wanted to modify annoying evidence written in the Ethereum blockchain. To do this, all users having a server on which this proof was written would have had to accept the modification. This was not the case and the users were forced to create a new blockchain based on a prior date to the annoying evidence they wanted to modify. This gave two totally autonomous blockchains called Ethereum classic ETC (keeping the annoying proof) and Ethereum ETH (implementing the modification). This example show how difficult it is to modify an blockchain anchoring proof.