The electronic signature

The electronic signature is a set of electronic data that accompany or are associated with an electronic document and whose basic functions are:

• Identify the signatory unequivocally.
• Ensure the integrity of the signed document. It ensures that the signed document is exactly the same as the original and that it has not been altered or manipulated.
• Ensure the non-repudiation of the signed document. The data used by the signer to make the signature are unique and exclusive and, therefore, subsequently, you cannot say that you have not signed the document.

The legal basis for electronic signatures is currently regulated by Regulation (EU) No 910/2014, known as the eIDAS Regulation, which establishes a common framework for electronic signatures, trust services and electronic identification throughout the European Union. In Spain, this regulation is complemented by Law 6/2020, on trusted electronic services, which make it possible to carry out legal transactions through electronic means, guaranteeing the security and reliability of these. They include the creation, verification and validation of electronic signatures, time stamps, certified electronic delivery services, among others.

To sign a document it is necessary to have a digital certificate or an electronic ID card.

The electronic certificate or the electronic DNI contains cryptographic keys that are the necessary elements to sign. Electronic certificates are intended to unambiguously identify their holder and are issued by Certification Service Providers.

You can learn more about certificates in the Electronic Certificates section.

The basic process followed for electronic signatures is as follows:

• The user has an electronic document (a spreadsheet, a pdf, an image, even a form on a web page) and a certificate that belongs to him and identifies him.
• The application or digital device used for the signature summarizes the document. The summary of a large document can be as simple as a few lines. This summary is unique and any modification of the document also involves a modification of the summary.
• The application uses the private key to encode the summary.
• The application creates another electronic document that contains that encoded summary. This new document is the electronic signature.

The result of this whole process is an electronic document obtained from the original document and the signer’s keys. The electronic signature, therefore, is the same resulting electronic document.

Some of the questions that may arise in the above process are:

• What tool should I use to sign?
• Do I need to install something on my computer?
• And when I sign a form on the internet, should I install something or does my browser already do everything automatically?
• How do I use the electronic ID from my computer? How do I install the DNI reader?

Since we are talking about an electronic signature, the signature must be made compulsorily by electronic means and you can make it in two ways:

• Downloading an application on your PC: In this case you use to sign the application that you install on your computer and you do not need to be connected to the internet. The application to use is AutoMarca, from the Ministry of Finance and Public Administrations. You can see more information about this, and download it in the Signature Applications section.
• Sign directly on the internet: This option is used especially when you sign forms or applications, for example, in the relationship with the Public Administration. But you can also sign your own documents on the internet using the service offered by VALIDe. To sign, you must download a component that works on the same browser.

In both cases you need to have an electronic certificate. In the Browsers and Computer section you can find instructions on how to install your certificate. And on the DNIe Electronic page you will find a section on the installation of the DNIe reader and its use.

It provides three characteristics in Internet communication: identification of the signer, data integrity and non-repudiation.

But apart from that, the practical applications of it are many and varied.

In general, they are oriented to carry out operations on the Internet that in everyday life require a signature to validate them.

Some examples of operations that can be performed currently using the digital signature are:

• Realization of the Income Declaration through the Internet.
• Requests in Electronic Administrative Records
• Request for working life.
• Reception of electronic notifications.
• Signature of e-mails.
• Signature of electronic invoices.

If we receive a signed document we are interested in validating the signature, that is, checking that the signed data corresponds to the originals, that the certificate with which it has been signed is valid and that the structure of the file is correct.

How do we know if a signature is valid?

We can check the validity of the signature of a document, see who is the signer and the signed document in VALIDe.