An Efficient Threshold Key-Insulated Signature Scheme

To tackle the key-exposure problem in signature settings,this paper introduces a new cryptographic primitive named threshold key-insulated signature(TKIS) and proposes a concrete TKIS scheme.For a TKIS system,at least k out of n helpers are needed to update a user’s temporary private key.On the one hand,even if up to k 1 helpers are compromised in addition to the exposure of any of temporary private keys,security of the non-exposed periods is still assured.On the other hand,even if all the n helpers are compromised,we can still ensure the security of all periods as long as none of temporary private keys is exposed.Compared with traditional key-insulated signature(KIS) schemes,the proposed TKIS scheme not only greatly enhances the security of the system,but also provides flexibility and efficiency.