General Properties of Quantum Bit Commitments (Extended Abstract)

Jun Yan, Jian Weng, Dongdai Lin +1 more

Jun Yan

Anthony J. Short, Nicolas Gisin, Sandu Popescu

Horace P. Yuen

Bit commitment involves the submission of evidence from one party to another so that the evidence can be used to confirm a later revealed bit value by the first party, while the second party cannot determine the bit value from the evidence alone. It is widely believed that secure quantum bit commitment is impossible due to quantum entanglement cheating, which is codified in a general impossibility theorem. In this paper, the scope of this general impossibility proof is extended and analyzed, and gaps are found. Three specific protocols are described for which the entanglement cheating as given in the impossibility proof fails to work. One of these protocols, QBC2, is proved to be unconditionally secure.

Jeffrey Bub

Yaqi Song, Li Yang

A semi-counterfactual quantum bit commitment (SCQBC) protocol is presented here for the first time, which makes use of counterfactual property. Similar to a counterfactual quantum key distribution scheme, half-photons are not transmitted through the quantum channel in our proposed protocol. In the SCQBC protocol, Bob, the verification party of the quantum bit commitment (QBC), sends the states while Alice, the commitment party, receives. Since Alice cannot receive all the states and entangle the commit bits with the verifier's registers, it is not subject to Mayers' and Lo-Chau's no-go theorem. In addition, a general bit commitment framework can be extracted from the SCQBC scheme, which opens up a new class of cryptographic protocols in counterfactual cryptography.