Strongly Secure Ramp Secret Sharing Schemes from Any Linear Secret Sharing Schemes

A secret sharing scheme (SSS) is a cryptographic tool to protect a secret from loss and leakage by dividing it into shares. A ramp SSS can improve the efficiency in terms of the sizes of shares by allowing partial information about the secret to leak out. In order to prevent the partial information from being recovered explicitly, the notion of the strong security has been introduced. However, there have been proposed few methods to construct strongly secure ramp SSSs for general access structures and they are not always sufficient. In this paper, we show that any linear ramp SSS can be transformed into a strongly secure scheme with the same access structure preserving the information ratio.