Shahrooz Janbaz - Electrical and computer faculty, Malek Ashtar University of Technology, Tehran, Iran
Bagher Bagherpour - Department of Mathematics and Cryptography, Malek Ashtar University of Technology, Isfahan, Iran
Ali Zaghian - Department of Mathematics and Cryptography, Malek Ashtar University of Technology, Isfahan, Iran

‎The characterization of the ideal access structures is one of the main open problems in secret sharing and is important from both practical and theoretical points of views‎. ‎A graph-based $۳-$homogeneous access structure is an access structure in which the participants are the vertices of a connected graph and every subset of the vertices is a minimal qualified subset if it has three vertices and induces a connected graph‎. ‎In this paper‎, ‎we introduce the graph-based $۳-$homogeneous access structures and characterize the ideal graph-based $۳$-homogeneous access structures‎. ‎We prove that for every non-ideal graph-based $۳$-homogeneous access structure over the graph $G$ with the maximum degree $d$ there exists a secret sharing scheme with an information rate $\frac{۱}{d+۱}$‎. ‎Furthermore‎, ‎we mention three forbidden configurations that are useful in characterizing other families of ideal access structures‎.

‎Cryptography‎, ‎Secret sharing‎, ‎Ideal access structures‎, ‎Graph-based access structures‎, ‎۳-homogeneous access structures