Danial Shiraly; Nasrollah Pakniat; Ziba Eslami
Abstract
Public key encryption with keyword search (PEKS) is a cryptographic primitive designed for performing secure search operations over encrypted data stored on untrusted cloud servers. However, in some applications of cloud computing, there is a hierarchical access-privilege setup among users so that upper-level ...
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Public key encryption with keyword search (PEKS) is a cryptographic primitive designed for performing secure search operations over encrypted data stored on untrusted cloud servers. However, in some applications of cloud computing, there is a hierarchical access-privilege setup among users so that upper-level users should be able to monitor data used by lower-level ones in the hierarchy. To support such situations, Wang et al. introduced the notion of hierarchical ID-based searchable encryption. However, Wang et al.'s construction suffers from a serious security problem. To provide a PEKS scheme that securely supports hierarchical structures, Li et al. introduced the notion of hierarchical public key encryption with keyword search (HPEKS). However, Li et al.'s HPEKS scheme is established on traditional public key infrastructure (PKI) which suffers from costly certificate management problem. To address these issues, in this paper, we consider designated-server HPEKS in identity-based setting. We introduce the notion of designated-server hierarchical identity-based searchable encryption (dHIBSE) and provide a formal definition of its security model. We then propose a dHIBSE scheme and prove its security under our model. Finally, we provide performance analysis as well as comparisons with related schemes to show the overall superiority of our dHIBSE scheme.
Sorour Sheidani; Ziba Eslami
Abstract
Nowadays, from one hand multimedia authentication techniques are widely used to achieve trustworthiness, on the other hand, due to the rapid growth of image processing software technologies, having a secure method to protect the copyright of these data seems fairly essential. Multipurpose watermarking ...
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Nowadays, from one hand multimedia authentication techniques are widely used to achieve trustworthiness, on the other hand, due to the rapid growth of image processing software technologies, having a secure method to protect the copyright of these data seems fairly essential. Multipurpose watermarking emerged in order to simultaneously accomplish multimedia authentication and copyright protection. In this paper, we propose a multipurpose watermarking method which achieves perfect security, the ability to detect tampered areas of the watermarked image as well as a lower BER rate, at the cost of reducing capacity by half. This watermarking scheme is blind in the sense that on the receiver side, neither the original host image nor the embedded watermark is needed for ownership watermark extraction or tamper detection. Experimental results show that our method is able to reconstruct extracted tampered watermarks even after various attacks such as JPEG compression, average filtering, gamma correction, median filtering, speckle noise, JPEG compression, sharpening, Wiener filter, and median filtering. Comparisons are provided with other multipurpose watermarking methods which primarily aim at simultaneous goals of copyright protection and authentication. We also show the superiority of our proposed method to three watermarking methods attaining these objectives on a one-goal-at-a-time basis.