Humanity has been using notarization since the time of the Sumerians, for various purposes:
In the digital world “time validation” or “timestamp” is a set of data which demonstrates the existence of a file starting from a certain moment in time, in a legally valid way and binding to third parties.
The “time validation” is very often used to guarantee the verification of an electronic signature afterwards, even when the certificate has been revoked or has expired.
The time validation on blockchain has characteristics that make it complementary to the traditional Timestamp, especially for long-term conservation. There is no fixed expiration date since in principle the blockchain does not end.
It is based on a public register distributed in thousands of copies in the world, so its verification does not depend on the service of a single entity whose issuing may cease in the long term. The OpenTimestamps technology, chosen by Intesi Group, was designed to be able to integrate multiple time validation methods (different blockchains or distributed registers), with the possibility of cross validation.
Finally the currently used blockchain, the Bitcoin one, is already resistant to quantum computation attacks, which are today in their infancy, but which in the future could compromise the signature algorithms currently in use for traditional timestamps.
The eIDAS Regulation (No. 910/2014) defines electronic time validation as “a set of electronic data that links other data in electronic form to a specific time and date, so as to prove that the latter existed at that time“.
In addition to art. 41 states that electronic time validation “cannot be denied legal effects and admissibility as evidence in judicial proceedings for the sole reason of its electronic form or because it does not meet the requirements of qualified temporary electronic validation“.
On 7th February 2019 the Italian Parliament voted a law (DL 135/2018, art. 8-ter paragraph 3) according to which storing data on a blockchain will be a valid way to prove its existence on that date. In Italy shortly it will be an operation similar to affixing a qualified time stamp or sending an electronic document via PEC.
“3. The memorization of an electronic document through the use of technologies based on distributed registers produces the legal effects of the electronic time validation referred to in Article 41 of Regulation (EU) n. 910/2014 of the European Parliament and of the Council, of 23 July 2014 ”.
This law obviously makes sense only if the distributed register (the blockchain) is secure, and cannot be tampered with. Today we have only one blockchain that for 10 years can objectively give guarantees of outstanding security and reliability: the Bitcoin blockchain. This is because the security on which it is based is thermodynamic, that is based on the fact that the miners spend around 49.5 TWh a year (2 billion euros) to produce the new blocks (the pages of its register).
In any case, OpenTimestamps is an “agnostic” technology with respect to the underlying blockchain. This means that it could work with any blockchain that has similar or better features and functionality than Bitcoin.
The use involves three basic operations: stamp, upgrade and verify.
The creation (stamp) of the time stamp generates a file with extension ots. This stamp is not immediately verifiable, since it only certifies the request made to the calendar server, which requires a few hours before being definitively registered on the blockchain.
The update (upgrade) of the time stamp, allows to add to the file with extension ots the complete information provided by the calendar server, which allow to trace back the ash of the original file to a precise block of the blockchain.
The verification (verify) of the time stamp consists of two parts. The first part is carried out locally and concerns the data present in the ots file up to the merkleroot. The second part consists in verifying the presence of the merkleroot in a specific block of the blockchain.
The merkleroot check is delegated to the calendar server, but if you have a full node it can also be done in complete autonomy. Not having a full node it is however possible to do a manual check by consulting one of the many block explorers present on line.