Secure secret reconstruction and multi-secret sharing schemes with unconditional security

In Shamir’s (t, n) secret sharing (SS) scheme, the secret s is divided into n shares by a dealer and is shared among n shareholders in such a way that any t or more than t shares can reconstruct this secret; but fewer than t shares cannot obtain any information about the secret s. In this paper, we will introduce the security problem that an adversary can obtain the secret when there are more than t participants in Shamir’s secret reconstruction. A secure secret reconstruction scheme, which prevents the adversary from obtaining the secret is proposed. In our scheme, Lagrange components, which are linear combination of shares, are used to reconstruct the secret. Lagrange component can protect shares unconditionally. We show that this scheme can be extended to design a multi-secret sharing scheme. All existing multi-secret sharing schemes are based on some cryptographic assumptions, such as a secure one-way function or solving the discrete logarithm problem; but, our proposed multi-secret sharing scheme is unconditionally secure. Copyright © 2013 John Wiley & Sons, Ltd.