Sharing Data Spaces in federated ecosystems can bring several advantages to companies and administrations. However, data security, privacy, and ethics issues need to be properly managed. In particular, pseudonymization techniques allow hiding portions of data accordingly to the access policies of the Federation. In this work, we deal with pseudonymization in Federated Data Spaces, providing an overview of the available approaches in the literature and our solution to create multi-level pseudonymization functionalities able to map different access policies in the same Federation.