Organizer: CROSSING, Prof. Gernot Alber
Entity authentication is one of the main cryptographic tasks. The development of cloning-resistant entity authentication protocols (EAPs) is of particular importance for the field, and optical schemes are currently considered to be among the most prominent candidates. In such schemes authentication relies on the optical response of physical disordered keys that are materialized by optical multiple-scattering media.
In the first part of my talk, I will discuss the main principles underlying some of the optical EAPs that have been presented in the literature so far, and I will address some of their fundamental aspects. In the second part of my talk, I will discuss a continuous-variable quantum EAP that we proposed recently. In our scheme the authentication relies on the optical response of the key, when probed by randomly selected coherent states of light, and the use of standard wavefront-shaping techniques that direct the scattered photons coherently to a specific target mode at the output. The quadratures of the electromagnetic field of the scattered light at the target mode are analysed using a homodyne detection scheme, and the acceptance or rejection of the key is decided upon the outcomes of the measurements. The proposed scheme can be implemented with current technology and offers collision resistance and robustness against key cloning.