Unconditionally Secure Qubit Commitment Scheme Using Quantum Maskers
Seok Hyung Lie, Hyukjoon Kwon, Myung-Gun Kim, Hyunseok Jeong · arXiv (Cornell University) · 2019
A commitment scheme allows one to commit to hidden information while keeping its value recoverable when needed. Despite considerable efforts, an unconditionally and perfectly secure bit commitment has been proven impossible both classically and quantum-mechanically. The situation is similar when committing to qubits instead of classical bits as implied in the no-masking theorem [K. Modi et al., Phys. Rev. Lett. {\bf 120}, 230501 (2018)]. In this Letter, we find that circumvention of the no-masking theorem is possible with the aid of classical randomness. Based on this, we construct an unconditionally secure quit-commitment scheme that utilises any kind of universal quantum maskers with optimal randomness consumption, which is distributed by a trusted initializer. This shows that randomness, which is normally considered only to obscure the information, can benefit a quantum secure communication scheme. This result can be generalised to an arbitrary dimensional system.