Multi-image encryption by circular random grids

  • Authors:

  • Tzung-Her Chen;Kuang-Che Li

  • Affiliations:

  • Department of Computer Science and Information Engineering, National Chiayi University, Chiayi City 60004, Taiwan;Department of Computer Science and Information Engineering, National Chiayi University, Chiayi City 60004, Taiwan

  • Venue:
  • Information Sciences: an International Journal
  • Year:
  • 2012

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Abstract

Visual secret sharing (VSS) can encode a secret image into several share images where the original secret can be reconstructed and recognized by sight by stacking all share images. There are two categories of VSS schemes: visual cryptography (VC) and random grids (RG). VC has three main drawbacks: the large size, the need for the codebook to be redesigned for specific applications, and the ability to encode only one secret image at a time. RG removes the first two drawbacks. This paper proposes a novel RG-based VSS scheme that encodes multiple secret images at a time. The scheme encrypts multiple secret images into two circular cipher-grids and decrypts the images by stacking two circular cipher-grids to obtain the first secret and gradually rotating one circular cipher-grid at a fixed degree (based on the quantity of the secret images encrypted) to disclose other secrets. Compared with conventional VC-based VSS, the proposed scheme has no pixel expansion, a higher capacity for secret sharing, and no need for a complex VC codebook to be redesigned. Theoretical analysis of visual quality and security is demonstrated.