Quantum communication uses 'entangled' states of particles that may be located at a large distance from one another but which are nevertheless coupled to each other. Florian Speelman stated: "With teleportation attacks, a group of cooperating attackers shares a quantum system with entangled states. I proved that a certain category of proposed protocols - ones that can be written as small quantum circuits - is not safe, not even for practical attacks. For example, we have made an effective attack on the 'Interleaved Product Protocol for position verification'. The challenge is now to find what protocols will be safe."
Besides his research on position-based quantum cryptography Florian Speelman investigated in an international team the possibilities of 'catalytic memory'. Catalytic memory is a method of calculation that 'uses memory without using it'. Here, the computer makes a calculation for which it uses memory that is already completely full, and it returns that memory to its original state after its use. The team showed in 2014 that this is possible and that it gives rise to a new way of thinking about memory usage with applications in cryptography. That using already-full memory gives extra computational power is counter intuitive and was thought to be impossible.
The PhD research of Florian Speelman was carried out at CWI in the Algorithms and Complexity research group, partly under the auspices of the QuSoft research center for quantum software in Amsterdam. His promotor is Prof. Harry Buhrman (CWI and UvA).