Theodosis has a BA/MA (Honors) in Mathematics: University of Cambridge, UK, a Master of Advanced Study in Mathematics (Number Theory Group): University of Cambridge, UK, a Master of Research (MRes) in Security Science from University College London (UCL) and a PhD in Information Security and Cryptography from University College London (UCL). His PhD was fully funded by the UCL SECReT program and EPSRC.

His has numerous awards in mathematics, physics and technology in PanCyprian level competitions and he was four times member of the National Team representing Cyprus in International and Balkan Mathematical competitions. He is recipient of the UK University Cipher Champion 2013 award, a 4-month intensive competition in code breaking.

His research interests lie in the area of cryptanalysis of both symmetric and asymmetric cryptosystems, information security, optimization techniques in cryptanalysis, blockchain and applications of data analytics techniques in fraud prevention.

Theodosis has experience in both academia and industry. He has taught courses at postgraduate level at University College London (UCL) related to security science and he had worked as a Cryptologist in a project funded by Technology Strategy Board (TSB) and as a Security SME at Digital Security and Fraud at Lloyds Banking Group in London, UK. He has experience working with big companies and organisations such as Lloyds Bank, Lloyds Maritime Academy, US Navy, European Central Bank (ECB), MSC SHIPMANAGEMENT and many others. 

He currently serves as Managing Director & Partner at Electi Consulting and an Industry Associate at UCL CBT. Electi is a consulting firm that uses AI, Blockchain and Cryptography to help their clients to reach their potential.