VISUAL CRYPTOGRAPHY SCHEME ON GRAPH ACCESS STRUCTURES WITH OPTIMAL PIXEL EXPANSION FOUR

Abstract

The strong access structure obtained from graph G is Gamma(G) if G = (V, E) is a connected graph. A visual cryptography scheme (VCS) is a specific technique for encoding a secret image that typically changes any pixel in the image to m subpixels for a group of active participants. Within each VCS, only qualified sets can retrieve the secret picture by stacking their preferred shares. The pixel expansion value is traditionally called m, and the minimum pixel expansion value of a VCS for Gamma(G) is referred to as m*(G). The principal aim of this paper is to identify all connected graphs G with m*(G) = 4 and omega(G) = 6, which realistically is the clique number of graph G.