Distributed Image Steganography (DIS) is a method of hiding secret information in multiple carrier images, making it more difficult to trace than conventional steganographic techniques, and requiring a collection of affected images for the retrieval of the secret data. In this paper we concentrate on performing DIS on grayscale images using Block-DCT (Discrete Cosine Transformation). Distributed Image Steganography using Block-DCT adds to the security of DIS by embedding the secret data in the Frequency Domain. This makes the carrier images more immune to various steganalysis attacks as the secret data is more evenly distributed amongst the pixels of the carrier images making it more difficult to determine its existence. We use parity check in order to compensate for round-off errors that are typically associated with DCT.

Secret sharing schemes are being widely used to distribute a secret between various participants so that an authorized subset of participants belonging to appropriate access structures can reconstruct this secret. However, a dealer might get corrupted by adversaries and may influence this secret sharing or the reconstruction process. Verifiable secret sharing (VSS) overcomes this issue by adding a verifiability protocol to the original secret sharing scheme. This article proposes a computationally secure publicly verifiable secret sharing scheme based on the three‐dimensional cellular automata (3D‐CA). Unlike the more widely used linear secret sharing schemes or secret sharing scheme based on the Chinese remainder theorem, our proposed scheme performs the secret sharing using 3D‐CA. The secret is considered one of the initial configurations of the 3D‐CA, and the following configurations are devised to be the shares distributed among the participants. Update mechanisms and various rules make it hard for an adversary to corrupt or duplicate a share. To make it even more efficient, we have added a verifiability layer such that a dealer posts a public share and private share to each shareholder. The verifiability layer reduces the interaction between dealer and participants and hence increases the security. The randomness of the shares has been calculated using the National Institute of Standards and Technology statistical test suite.

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In secret sharing, a secret is distributed between various participants in a manner that an authorized group of participants in the appropriate access structures can recover this secret. However, a dealer might get corrupted by adversaries and may influence this secret sharing or the reconstruction process. Verifiable secret sharing (VSS) overcomes this issue by adding a verifiability protocol to the original secret sharing scheme. This chapter discusses a computationally secure publicly verifiable secret sharing scheme constructed using the three-dimensional cellular automata (3D CA). The initial configuration of the 3D CA is the secret. The following configurations are devised to be the shares distributed among the participants. Update mechanisms and various rules make it hard for an adversary to corrupt or duplicate a share. To make it even more efficient, the authors added a verifiability layer such that a dealer posts a public share and a private share to each shareholder. The NIST test suite has been used to calculate the randomness of the shares.