Security Notes on Two Cheat-Proof Secret Sharing Schemes

In (t, n) secret sharing schemes, a dealer splits a secret into n shares and sends a share to each of n participants. If necessary, any t share holders can provide their secret shares together and then recover the secret by using a publicly specified algorithm. In the secret recover phase of such schemes, how to detect the cheating from share holders is an important technical issue. Based on RSA cryptosystem and one-way function, Fei, et al. recently proposed two cheat-proof secret sharing schemes. However, it is shown that in fact their schemes do not provide the function of cheat-proof. The reason is that malicious share holders can easily forge false shares such that the authenticating equality is satisfied. The result is that honest participants will be cheated and misled to believe that the recovered secret is correct.