Abstract: Privacy-preserving signed distance is a special case of secure multi-party computation problem and it can be applied in many fields such as military and commercial fields.Calculating the sign of the signed distance decision space geometric object’s position is an essential method of processing spatial geometric object position.In this paper，one privacy-preserving signed distance protocol is presented to solve the signed distance problem based on scalar product protocol.The security and correctness of the protocol are also discussed.And then the privacy-preserving of the triangle intersection with the plane determines is taken as the example to explain its application.

Key words: privacy-preserving, security multi-party computation, signed distance, computational geometry, protocol

摘要： 保护私有信息的符号距离的判定是一个特殊的安全多方计算问题，可以应用到军事、商业等诸多领域，通过计算符号距离的符号来判定空间几何对象的位置是处理空间几何对象的位置问题的一个基本方法。基于点积协议，提出了一个保护私有信息的符号距离判定协议，解决了符号距离的判定问题，然后讨论和分析了协议的安全性与正确性，并且以保护私有信息的三角形与平面相交判定为例说明了其应用。

关键词: 隐私保护, 安全多方计算, 符号距离, 计算几何, 协议