Emmanuel Zambrini Cruzeiro

We present a novel entanglement-based protocol for chosen-input 1-out-of-2 Quantum Oblivious Transfer (QOT) together with a practical experimental implementation. The protocol relies on the non-commuting encoding properties of Bell states, and it requires minimal interaction between parties, with quantum communication in only one direction. Under the assumptions of the Noisy Quantum Storage Model, the protocol provides epsilon-secure OT that can serve as a primitive for two-party computation schemes such as Yao's garbled circuits. For standard security parameters, our proof-of-principle experiment achieves OT-key generation rates of 0.225 bits per second.

Few primitives are as intertwined with the foundations of cryptography as Oblivious Transfer (OT). Not surprisingly, with the advent of quantum resources in information processing, OT played a central role in establishing new possibilities (and defining impossibilities) pertaining to the use of these novel assets. A major research path is minimizing the required assumptions to achieve OT, and studying their consequences. Regarding its computation, it is impossible to construct unconditionally-secure OT without extra assumptions; and, regarding communication complexity, achieving one-shot (and even non-interactive) OT has proved to be an elusive task, widely known to be impossible classically. In this work, we devise a extit{one-shot OT}, showig how this construction is indeed possible using quantum resources, if we assume the existence of one-way functions and sequential functions in the Noisy-Quantum-Storage Model.

Device-independence (DI) is the golden standard for quantum key distribution (QKD) security: it allows unconditional security based on the laws of physics even for untrusted or maliciously designed devices. Nevertheless, DI-QKD, for now, remains extremely challenging. The first proof-of-principle experiments having been performed only very recently, almost 40 years after the invention of BB84. It then becomes naturally interesting to study scenarios which may reach a compromise between experimental challenge and security: for example, by assuming than the users have a partial description of the devices. This intermediate scenario is called semi-device-independent (SDI) QKD and aims for a reasonable trade-off between the highest level of security, device-independence, and experimental feasibility.

Quantum communication ensures security by using quantum mechanics, typically through Quantum Key Distribution (QKD) which is limited to a few hundred kilometers for useful secret key rates. This study examines Quantum Keyless Private Communication (QKPC), inspired by the classical wiretap model, which allows secure one-way communication without shared keys. Two implementations are explored: the original On-Off Keying (OOK) and a new polarization-based version. Both methods are implemented experimentally and the results confirm their effectiveness and potential as practical alternatives to traditional QKD for secure, long-distance communication.