The complexity and randomness of linear multi-secret sharing schemes with non-threshold structures

In a linear multi-secret sharing scheme with non-threshold structures, several secret values are shared among n participants, and every secret value has a specified access structure. The efficiency of a multi-secret sharing scheme is measured by means of the complexity σ and the randomness τ. Informally, the complexity σ is the ratio between the maximum of information received by each participant and the minimum of information corresponding to every key. The randomness τ is the ratio between the amount of information distributed to the set of users U = {1, ⋯, n} and the minimum of information corresponding to every key.In this paper, we discuss σ and τ of any linear multi-secret sharing schemes realized by linear codes with non-threshold structures, and provide two algorithms to make σ and τ to be the minimum, respectively. That is, they are optimal.