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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)
Copyright q 2010 Gejun Bao et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. We determine the condition on α, μ, β, and λ for which | 1−α z/f z μ α zf ′ z /f z z/f z − 1| < λ implies f z(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)
In 2004, Hwang and Chen demonstrated new multi-proxy multi-signature schemes that allow a group of authorized proxy signers to sign messages on behalf of a group of original signers. Later, Lyuu and Wu pointed out Hwang et al.’s schemes were not secure and then proposed a modified scheme. They claimed that their modified schemes were secure. But in this(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) thresholdmutisignature 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)