乘性单调张成方案（或乘性的线性密钥共享体制）是设计安全多方计算协议的一个重要
工具。本文给出了一个单调张成方案（或线性密钥共享体制）具有乘性的充分必要条件，即通过判断
一个线性方程组是否有解可以确定一个单调张成方案是否具有乘性。作为例子，我们研究了Shamir的
门限密钥共享体制以及带权重的门限密钥共享体制，指出了它们具有乘性时所应具备的条件。

Multiplicative monotone span program (or multiplicative linear secret sharing scheme)
is a important tool for building a multi-party computation protocol。In this paper, we give a necessary
and su±cient condition for a monotone span program (or linear secret sharing scheme) to be multiplica-
tive，i.e., we can decide whether a monotone span program is multiplicative by judging if a system of
linear equations is solvable. As examples, we study Shamir’s threshold secret sharing scheme and the
extended threshold scheme with weights, pointing out when they are multiplicative, respectively.