A Novel Approach for Robust Perceptual Image Hashing

Perceptual image hashing system generates a short signature called perceptual hash attached to an image before transmission and acts as side information for analyzing the trustworthiness of the received image. In this paper, we propose a novel approach to improve robustness for perceptual image hashing scheme for generating a perceptual hash that should be resistant to content-preserving manipulations, such as JPEG compression and Additive white Gaussian noise (AWGN) also should differentiate the maliciously tampered image and its original version. Our algorithm first constructs a robust image, derived from the original input by analyzing the stability of the extracted features and improving their robustness. From the robust image, which does perceptually resemble the original input, we further extract the final robust features. Next, robust features are suitably quantized allowing the generation of the final perceptual hash using the cryptographic hash function SHA1. The main idea of this paper is to transform the original image into a more robust one that allows the extraction of robust features. Generation of the robust image turns out be quite important since it introduces further robustness to the perceptual image hashing system. The paper can be seen as an attempt to propose a general methodology for more robust perceptual image hashing. The experimental results presented in this paper reveal that the proposed scheme offers good robustness against JPEG compression and Additive white Gaussian noise.

A Short Server-Aided Certificateless Aggregate Multisignature Scheme in the Standard Model

Aggregate signature scheme allows each signer to sign a different message and then all those signatures are aggregated into a single short signature. In contrast, multisignature scheme allows multisigners to jointly sign only one message. Aggregate multisignature scheme is a combination of both aforementioned signature schemes, where signers can choose to generate either a multisignature or an aggregate signature. This combination scheme has many concrete application scenarios such as Bitcoin blockchain, Healthcare, Multicast Acknowledgment Aggregation, and so on. On the other hand, to deal with the problems of expensive certificates in certified public key cryptography and key escrow in identity-based cryptography, the notion of certificateless public key cryptography has been introduced by Riyami and Paterson at Asiacrypt’03. In this paper, we propose the first certificateless aggregate multisignature scheme that achieves the constant-size of signature and is secure in the standard model under a generalization of the Diffie-Hellman exponent assumption. In our scheme, however, the signature is generated with the help of the authority.