Leonardo's papers: - [Self-certified Sybil-free pseudonyms](https://dl.acm.org/citation.cfm?doid=1352533.1352558) - [A Self-certified and Sybil-Free Framework for Secure Digital Identity Domain Buildup](https://link.springer.com/chapter/10.1007%2F978-3-540-79966-5_5) - [Sybil-Free Pseudonyms, Privacy and Trust: Identity Management in the Internet of Services](https://www.jstage.jst.go.jp/article/ipsjjip/19/0/19_0_317/_article)