Steganography is the science of hiding secure data in digital carriers such as images and videos. Pixel value differencing (PVD) steganography algorithms embed data into images depending on pixel neighborhood differences. We have proposed PVD scheme for embedding secure data into digital images. The image is divided into non‐overlapping 3 × 3 blocks. The block's median pixel is used as a reference for calculating pixel differences. The distance between the minimum and maximum differences are fine tuned for spreading the secure data on a wide range of image regions with high‐intensity fluctuations. The embedding procedure embeds secure data into the content regions with edges and intensity transitions. Texture images provide higher embedding size compared with regular images. The results showed that the proposed algorithm is successfully able to avoid smooth regions in the embedding process. In addition, the proposed algorithm shows better embedding quality compared with the state of the art PVD approaches especially with low‐embedding rates. Copyright © 2016 John Wiley & Sons, Ltd.

Abstract

Previous contract protocols in blockchains ensure their fairness and traceability by utilizing centralized credible nodes. If credible nodes are dishonest or conspire with the signatory, then other nodes are compromised. Meanwhile, the leakage of sensitive information of participant nodes poses a serious threat to the privacy security of data access in blockchains. To address this issue, this study proposes a secure control method of digital certificate-based data access in blockchains. The proposed method combines blockchain and digital certificate technologies and designs a secure authentication protocol for privacy data in blockchains without verifying the encrypted identity signature of the third-party participant. The highefficiency network forwarding protocol proposed in this work can support the fair contract signing of multiple signers via blockchain. This protocol can protect the privacy of contracts and identities of participants. Experimental results show that the proposed scheme is superior in terms of communication overhead, storage overhead, and detection rate.

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