Citizen Attention with Decentralised Identity Models (ACID)

Project completed in December 2025.

Context and objectives of the project

The ACID project (Citizen Services using Decentralised Identity Models), financed by European Union NextGeneration-EU, the Recovery Plan, Transformation and Resilience, through INCIBE, and developed in collaboration with the Gradiant Technology Centre, aimed to develop a decentralised digital identity system with the following characteristics:

Universal, portable, usable and scalable, based on open standards.
A self-sovereign system, in which end users would have complete control over their digital identity
Privacy-assured, in accordance with European standards and regulations.
Secure, using advanced cryptographic techniques to validate the exchange of credentials between end-users, identity issuers and service providers.

Scope of the project

The identity solution developed is aimed at both public bodies and private companies, with the aim of providing a new mechanism for managing specific attributes of a citizen’s identity.

Among the activities carried out to ensure the proper management of the portfolio, the necessary developments were implemented for the issuance, storage, verification and revocation of credentials via a web interface. It also allows for the definition of specific credentials for each procedure and the selective disclosure of portfolio attributes.

Two portfolios were developed: one for individual users and another for corporate environments, aimed at legal entities.

The developments are compatible with the European Blockchain Services Infrastructure (EBSI) and its digital identity model (ESSIF).

Comprehensive services for citizens based on ACID

The digital identity solution developed as part of the project will be integrated with Councilbox’s Virtual Office for Citizen Service (OVAC), a product that enables procedures to be carried out with legal certainty, part of which involves verifying the identity of the individuals carrying them out.

The new identity model developed as part of the project will form part of the application’s suite of identification mechanisms, which also includes other, more ‘traditional’ methods used by public authorities, such as Cl@ve, the electronic ID card or digital certificates. With the new identity model, it will be possible to:

Identify and authenticate citizens through an identity credential defined by the EBSI network.
Issue the citizen with specific credentials depending on the procedure carried out that could be valid in different EU member states, such as a digital credential with the citizen’s European security number, a criminal record certificate or specific attributes of a person’s identity such as age.

Financed by European Union NextGeneration-EU, through INCIBE.