摘要：
The threshold t can be changed into t′(>t ) in (t→t′, n) threshold changeable schemes, which can increase the difficulty for attackers to attack the schemes. Based on Lagrange interpolation polynomial, two perfect threshold changeable multi-secret sharing schemes: (t→t+1, n) threshold changeable scheme Π,Π′ and (t→t+v-1, n) threshold changeable scheme 〈Π,Π″〉 are proposed. It is shown that Π′ is a (t-1, t+1, n) ramp secret sharing scheme,Π″ is an optimal (t-1, t+v-1, n) ramp secret sharing scheme and 〈Π,Π″〉 is an optimal (t→t+v-1, n) threshold changeable scheme.%(t→t′,n)门限可变方案研究如何将门限t改变为t′(>t)以增加攻击者攻击方案的难度.基于拉格朗日插值多项式提出两类完美的门限可变多秘密共享方案:(t→t+1,n)门限可变方案〈Π,Π′〉 、(t→t+v-1,n)门限可变方案〈Π,Π″〉,并证明 Π′是(t-1,t+1,n)ramp秘密共享方案,Π″是最优(t-1,t+v-1,n)ramp秘密共享方案,〈Π,Π″〉 是最优(t→t+v-1,n)门限可变方案.
