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Searchable encryption is an important cryptographic primitive that enables privacy-preserving keyword search on encrypted electronic medical records (EMRs) in cloud storage. Efficiency of such searchable encryption in a medical cloud storage system is very crucial as it involves client platforms such as smartphones or tablets that only have constrained(More)
It has always been a critical issue to find efficient methods for fast revocation of a user's identity in identity (ID)-based cryptosystems. Unfortunately, none of the previous ID-based cryptography can find a practical way. Libert et al. and Baek et al. respectively propose an ID-based mediated encryption scheme based on the practical ID-based encryption(More)
A nominative signature scheme allows a nominator (or signer) and a nominee (or verifier) to jointly generate and publish a signature in such a way that only the nominee can verify the signature and if necessary , only the nominee can prove to a third party that the signature is valid. In a recent work, Huang and Wang proposed a new nominative signature(More)
—A new ID-based group signature scheme, in which group managers and group members are all ID-based, is presented in this paper. Our scheme is obtained by using a new way to the construction of group signature schemes and based on an ID-based signature scheme from bilinear pairing. Due to the nice and simple constructive method and the sound properties of(More)
In 1999, Sun et al. proposed a new (t, n) threshold proxy signature scheme based on Zhang's threshold proxy signature scheme. But in 2003 Hsu et al. pointed out that Sun's scheme suffered from a drawback and demonstrated an improvement to counter it. In this paper we point out that Hsu's scheme suffers from an insider attack against their scheme. That is, a(More)
In [1], Li et al. proposed a new type of signature scheme, called the (t, n) threshold-mutisignature scheme. The first one needs a mutually trusted share distribution center (SDC) while the second one does not. In this paper, we present a security analysis on their second schemes. We point out that their second threshold-multisignature scheme is vulnerable(More)