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A group key agreement (GKA) protocol allows a set of users to establish a common secret via open networks. Observing that a major goal of GKAs for most applications is to establish a confidential channel among group members, we revisit the group key agreement definition and distinguish the conventional (symmetric) group key agreement from asymmetric group(More)
k-times anonymous authentication (k-TAA) schemes allow members of a group to be authenticated anonymously by application providers for a bounded number of times. Dynamic k-TAA allows application providers to independently grant or revoke users from their own access group so as to provide better control over their clients. In terms of time and space(More)
Identity-based cryptosystems have an inherent key escrow issue, that is, the Key Generation Center (KGC) always knows user secret key. If the KGC is malicious, it can always impersonate the user. Certificateless cryptography, introduced by Al-Riyami and Paterson in 2003, is intended to solve this problem. However, in all the previously proposed(More)
In this paper, we propose two new anonymous secure electronic voting schemes that protect the privacy of the voters and prevent double voting. These schemes do not require any special voting channel and the communications can occur entirely over existing networks such as the Internet. The proposed schemes are based on ElGamal digital signature algorithm and(More)
We present the first dynamic universal accumulator that allows (1) the accumulation of elements in a DDH-hard group G and (2) one who knows x such that y = g has — or has not — been accumulated, where g generates G, to efficiently prove her knowledge of such x in zero knowledge, and hence without revealing, e.g., x or y. We introduce the Attribute-Based(More)
Decentralized attribute-based encryption (ABE) is a variant of a multiauthority ABE scheme where each authority can issue secret keys to the user independently without any cooperation and a central authority. This is in contrast to the previous constructions, where multiple authorities must be online and setup the system interactively, which is impractical.(More)