## Cryptology ePrint Archive: Report 2009/196

**Analysis of one quantum bit string commitment**

*Zhengjun Cao*

**Abstract: ** A. Kent proposed a quantum bit string commitment protocol in 2003.
Not using the standard two conjugate states $|0\rangle$, $|1\rangle
$, $|+\rangle $ and $|-\rangle $, the protocol uses
$\psi_0=|0\rangle$ and $\psi_1=\sin \theta|0\rangle+\cos \theta
|1\rangle $, where $\theta\neq 0$. In this paper, we show that the
protocol can not guarantee security to the receiver.
$(1-\frac{\sin^2 \theta}{2})n $ bits are definitely exposed to the
receiver, where $n$ is the length of the committed string.

**Category / Keywords: **cryptographic protocols /

**Date: **received 27 Apr 2009

**Contact author: **zhencao at ulb ac be

**Available format(s): **PDF | BibTeX Citation

**Version: **20090510:210351 (All versions of this report)

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