Broadcast encryption (BE) schemes allow a sender to securely broadcast to any subset of members but requires a trusted party to distribute decryption keys. Group key agreement (GKA) protocols enable a group of members to negotiate a common encryption key via open networks so that only the members can decrypt the ciphertexts encrypted under the shared encryption key, but a sender cannot exclude ...

Secure group communication systems become more and more important in many emerging network applications. For a secure group communication system, an efficient and robust group key management approach is essential. In this paper, a new group key management approach with a group controller GC using the theory of hyper-sphere is developed, where a hyper-sphere is constructed for the group and each...

most of the studies on the key word method of second/foreign language vocabulary learning have been based on the evidence from laboratory experiments and have primarily involved the use of english key words to learn the vocabularies of other languages. furthermore, comparatively quite limited number of such studies is done in authentic classroom contexts. the present study inquired into the eff...

Especially for key establishment protocols to be used in internet applications, the (privacy) concern of deniability arises: Can a protocol transcript be used—possibly by a participant—to prove the involvement of another party in the protocol? For two party key establishment protocols, a common technique for achieving deniability is the replacement of signature-based message authentication with...

As a result of the increased popularity of group-oriented applications and protocols, group communication occurs in many different settings: from network multicasting to application layer teleand video-conferencing. Regardless of the application environment, security services are necessary to provide communication privacy and integrity. This thesis considers the problem of key management in a s...

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 key agreement (ASGKA) protocols. Instea...

Communication complexity has always been an important issue when designing group key distribution systems. This paper systematically studies what can be achieved for the most common measures of protocol complexity. Lower bounds for the total number of messages, the total number of exchanges, and the number of necessary rounds are established, whereby models that allow broadcasting have to be di...

Most of the studies on the key word method of second/foreign language vocabulary learning have been based on the evidence from laboratory experiments and have primarily involved the use of English key words to learn the vocabularies of other languages. Furthermore, comparatively quite limited number of such studies is done in authentic classroom contexts. The present study inquired into the eff...

In 2008, Wan et al. presented an anonymous ID-based group key agreement scheme for wireless networks, for which they claim that it ensures anonymity and unlinkability of the group members, as well as forward and backward secrecy of the group session key. In this paper, we show that forward and backward secrecy do not hold for the protocol. We propose a correction that introduces a shielding fac...