The IM building block allows identification, authentication, and authorisation of stakeholders operating in a data space. It ensures that organisations, individuals, machines, and other actors are provided with acknowledged identities, and that those identities can be authenticated and verified, including additional information provisioning1, to be used by authorisation mechanisms to enable access and usage control. The IM building block can be implemented on the basis of readily available IM platforms that cover parts of the required functionality. Examples of open-source solutions are the KeyCloak infrastructure51, the Apache Syncope IM platform52, the open-source IM platform of the Shibboleth Consortium53, or the FIWARE IM framework54. Integration of the IM building block with the eID building block of the Connecting Europe Facility (CEF)55, supporting electronic identification of users across Europe, would be particularly important. Creation of federated and trusted identities in data spaces can be supported by European regulations such as EIDAS.