Analysis of one quantum bit string commitment.
Zhengjun Cao · 2009
Abstract A. Kent proposed a quantum bit string commitment protocol in 2003. Not using the standard two conjugate states |0〉, |1〉, |+ 〉 and |−〉, the protocol uses ψ0 = |0 〉 and ψ1 = sin θ|0 〉 + cos θ|1〉, where θ ̸ = 0. In this paper, we show that the protocol can not guarantee security to the receiver. (1 − sin2 θ 2)n bits are definitely exposed to the receiver, where n is the length of the committed string.