Manuel Goulão

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.

Regarding minimal assumptions, most of classical cryptography is known to depend on the existence of One-Way Functions (OWFs). However, recent evidence has shown that this is not the case when considering quantum resources. Besides the well known unconditional security of Quantum Key Distribution, it is now known that computational cryptography may be built on weaker primitives than OWFs, e.g., pseudo-random states [JLS18], one-way state generators [MY23], or EFI pairs of states [BCQ23]. We consider a new quantum resource, pseudo-entanglement, and show that the existence of EFI pairs, one of the current main candidates for the weakest computational assumption for cryptography (necessary for commitments, oblivious transfer, secure multi-party computation, computational zero-knowledge proofs), implies the existence of pseudo-entanglement, as defined by [ABF+24, ABV23] under some reasonable adaptations. We prove this by constructing a new family of pseudo-entangled quantum states given only EFI pairs. Our result has important implications for the field of computational cryptography. It shows that if pseudo-entanglement does not exist, then most of cryptography cannot exist either. Moreover, it establishes pseudo-entanglement as a new minimal assumption for most of computational cryptography, which may pave the way for the unification of other assumptions into a single primitive. Finally, pseudo-entanglement connects physical phenomena and efficient computation, thus, our result strengthens the connection between cryptography and the physical world.

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.