Abstract

We first consider a protocol of entanglement-based bit escrow, whose security is quite easily analyzed by virtue of the monotonicity of entanglement. We then discuss the difficulty in developing secure cheat-sensitive quantum bit commitment (CSQBC) by showing examples of our trial-and-errors, such as a simple coding scheme and its similarity to CSQBC based on the combination of bit escrow and quantum coin flipping. Moreover, we discuss the (im)possibility of secure CSQBC from the viewpoint of the universal composable security of quantum coin flipping. http://arxiv.org/abs/quant-ph/0703099v3 http://arxiv.org/abs/quant-ph/0703099v5