Charles Guillemet joined Ledger in 2017 as Chief Security Officer and was promoted to Chief Technology Officer (CTO) in 2019. Before joining Ledger, he spent 10 years in the Cryptography & Hardware Security sector, starting with Tiempo, an innovative secure start-up where he designed EAL5+ secure integrated circuits. He then worked as Technical Manager in an Information Technology Security Evaluation Facility (ITSEF) at the CEA, the French Research Organization.