Cryptanalysis of Lattice-Based Threshold Changeable Multi-secret Sharing Scheme

In a secret sharing scheme (SSS), a secret is shared among a group of members such that if at least a fixed number of members (say t) join with their shares then they can get the secret back. This number t is called threshold of the scheme. Due to some security reasons, we may need to rise the threshold value t of the SSS without reconstructing the secret. In 2017, H. Pilaram and T. Eghlidos gave a technique to change the threshold of their earlier proposed lattice-based multi-stage SSS. In this paper, we gave an attack on their threshold changeable technique. We also modified their threshold changeable technique to overcome this attack.