Friendly progressive random-grid-based visual secret sharing with adaptive contrast

• A RG-based VSS scheme with friendliness and progressive secret-reconstruction.
• Theoretic analysis demonstrated its visual quality and security.
• Contrast-flexibility between reconstructed secrets and logo images is presented.

Visual secret sharing (VSS) schemes providing secret communication services are classified into two categories depending on the method of encoding the secret: visual cryptography (VC)-based and random grid (RG)-based schemes. A friendly progressive version of the VC-based VSS scheme was presented in 2008; however, it is marred by pixel expansion, which is the innate deficiency of conventional VC-based VSS schemes. This paper proposes a suitable user-friendly RG-based VSS scheme with progressive secret reconstruction and without pixel expansion. The experimental results of the developed scheme validated its feasibility, and a theoretical analysis demonstrated its visual quality and security.