Paper 2020/1077 Original: eprint.iacr.org/2020/1077 ↗

Unconditionally secure quantum bit commitment: Revised

Abstract

Bit commitment is a primitive task of many cryptographic tasks. It has been proved that the unconditionally secure quantum bit commitment is impossible from Mayers-Lo-Chau No-go theorem. A variant of quantum bit commitment requires cheat sensible for both parties. Another results shows that these no-go theorem can be evaded using the non-relativistic transmission or Minkowski causality. Our goal in this paper is to revise unconditionally secure quantum bit commitment. We firstly propose new quantum bit commitments using distributed settings and quantum entanglement which is used to overcome Mayers-Lo-Chau No-go Theorems. Both protocols are perfectly concealing, perfectly binding, and cheating sensible in asymptotic model against entanglement-based attack and splitting attack from quantum networks. These schemes are then extended to commit secret bits against eavesdroppers. We further propose two new applications. One is to commit qubit states. The other is to commit unitary circuits. These new schemes are useful for committing several primitives including sampling model, randomness, and Boolean functions in cryptographic protocols.