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.
Mohammad Ebrahim Ebrahimi Kiasari; Nasrollah Pakniat; Abdolrasoul Mirghadri; Mojtaba Nazari
Abstract
Secret sharing (SS) schemes allow the sharing of a secret among a set of trustees in such a way that only some qualified subsets of them can recover the secret. Ordinary SS schemes assume that the trust to each trustee is fixed over time. However, this is not the case in many real scenarios. Social secret ...
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Secret sharing (SS) schemes allow the sharing of a secret among a set of trustees in such a way that only some qualified subsets of them can recover the secret. Ordinary SS schemes assume that the trust to each trustee is fixed over time. However, this is not the case in many real scenarios. Social secret sharing (SSS) is a recently introduced type of SS that addresses this issue. It allows the sharing of a secret among a set of trustees such that the amount of trust to each participant could be changed over time. There exist only a few SSS schemes in the literature; most of them can share only one secret during each execution. Hence, these schemes lack the required efficiency in situations where multiple secrets need to be shared. According to the literature, there exists only one social multi-secret sharing (SMSS) scheme in which, all the secrets are reconstructed at one stage. However, in many applications, the secrets should be recovered in multiple stages and even according to some specified order. To address these problems, this paper employs Birkhoff interpolation method and Chinese remainder theorem and proposes a new SMSS scheme. In the proposed scheme, the shareholders can recover the secrets in different stages and according to the specified order by the dealer. The security analysis of the proposed scheme shows that it provides all the needed security requirements. In addition, the performance analysis of the proposed scheme indicates its overall superiority over the related schemes.