A modified CLIQUES key agreement protocol for secure multicast

In a secured multicast application, members may join or leave frequently. Hence, key management is one of the most challenging problems. A practical and scalable key management requires high security features, efficient key distribution, low key-storage cost, and small processing overhead. CLIQUES (1-5) scheme was proposed to handle contributory key agreement. It extends the two-party Diffie-Hellman (6) algorithm to allow a group of members to "agree" upon a symmetric group key. Among the existing key management approaches, CLIQUES has the lowest cost in establishing the common session key. It also imposes less processing overhead in the user machine. The main drawback of CLIQUES is that a large number of re-key messages have to be exchanged among members when there is a membership change. The number of messages exchanged is proportional to the size of the membership. Consequently, CLIQUES is not very scalable and cannot support large group of members. In this thesis, we proposed a Static CLIQUES, in which, a static group controller is introduced to reduce the complexity of status synchronization process within the group when there is a membership change. The number of keys stored in each member is smaller than that of the original CLIQUES. In addition, the use of static group controller provides member privacy protection since individual member does not have direct contact with other members. We also proposed a hierarchical CLIQUES structure to support a large number of members by sub-grouping them logically into a hierarchical key tree. It is more scalable than dynamic CLIQUES. The size of re-key message being distributed is found to be comparable with hierarchical key tree approach (7-11).

A modified CLIQUES key agreement protocol for secure multicast

In a secured multicast application, members may join or leave frequently. Hence, key management is one of the most challenging problems. A practical and scalable key management requires high security features, efficient key distribution, low key-storage cost, and small processing overhead. CLIQUES (1-5) scheme was proposed to handle contributory key agreement. It extends the two-party Diffie-Hellman (6) algorithm to allow a group of members to "agree" upon a symmetric group key. Among the existing key management approaches, CLIQUES has the lowest cost in establishing the common session key. It also imposes less processing overhead in the user machine. The main drawback of CLIQUES is that a large number of re-key messages have to be exchanged among members when there is a membership change. The number of messages exchanged is proportional to the size of the membership. Consequently, CLIQUES is not very scalable and cannot support large group of members. In this thesis, we proposed a Static CLIQUES, in which, a static group controller is introduced to reduce the complexity of status synchronization process within the group when there is a membership change. The number of keys stored in each member is smaller than that of the original CLIQUES. In addition, the use of static group controller provides member privacy protection since individual member does not have direct contact with other members. We also proposed a hierarchical CLIQUES structure to support a large number of members by sub-grouping them logically into a hierarchical key tree. It is more scalable than dynamic CLIQUES. The size of re-key message being distributed is found to be comparable with hierarchical key tree approach (7-11).

Membership change, idea generation, and group creativity: A motivated information processing perspective

Membership change has been found to stimulate collective idea generation but to not always benefit group creativity—the generation of final outcomes that are novel and useful. Based on motivated information processing theory, we propose that membership change challenges group members to generate more ideas, but that this only contributes to group creativity when members have high levels of prosocial motivation and are willing to process and integrate each other’s ideas. In a laboratory study of 56 student groups, we found that incremental, but not radical, idea generation mediated the positive effect of membership change on group creativity, and only when group members were prosocially motivated. The present study points to different roles of incremental versus radical ideas and underscores the importance of accounting for prosocial motivation in groups for reaping the benefits of membership change in relation to group creativity.

A Quantitative Study of the Role Shariah Boards and Bank Ownership Structures Play in Enhancing the Financial Performance of Islamic Banks: A Case of Pakistan

Shariah governance is a central feature and the second layer of corporate governance for Islamic banks (IBs) and Islamic financial institutions (IFIs). Shariah governance is unique to IBs and IFIs due to their possession of Shariah Supervisory Boards (SSB). SSBs serve to ensure that the management of Islamic banking institutions complies with shariah principles. Shariah governance is not only designed to raise the confidence of investors and the public in terms of authenticity and compliance to Islamic banking practices, but also to minimise the fiduciary and reputational risks of Islamic banking institutions. Due to the importance of shariah governance and the role of SSBs in IBs, this research investigates the role of SSBs in influencing the financial performance of IBs with the moderation role of ownership structure in Pakistan. By using nine years of data (2009-2017) pertaining to three Islamic banks in Pakistan, we found that shariah supervisory board reputations, expertise, cross membership, change in composition, shariah qualification, and ownership have significant moderation relationships with the financial performance of IBs. This study is an attempt to provide a deeper understanding of the role of owners and Shariah Supervisory Boards in enhancing the financial performance of Islamic banks for both researchers and policymakers.

Dynamic Membership Management in Anonymous and Deniable Distance Bounding

For secure location proof in many applications, distance bounding protocols are considered as one of the useful tools that can be used in practice. In distance bounding protocols, a prover and a verifier can measure the distance between them by performing an interactive protocol. In general, the verifier is regarded as an honest service provider, and thus, an adversarial verifier is not considered for security analysis. However, we cannot ignore the possibility of the corruption of the verifier, which can spoil the prover’s privacy. To handle the security problem, a prover-anonymous and deniable distance bounding protocol is proposed, which can guarantee the privacy of the prover even though the verifier is corrupted. In this paper, we review the prover-anonymous and deniable distance bounding protocol in terms of the membership management, and we show that the communication overhead in the protocol for each membership change is O(n) where n is the number of users. Then, we propose an improved membership management technique, which can efficiently support membership change in terms of the communication overhead. The improved technique requires O(1) for each membership change instead of O(n), as in the existing protocol.

Relationship Change, Network Change, and the Use of Single Name Generators in Longitudinal Research on Social Support

As relationships change and people change the kinds of support they provide, name generators that collect information about ties that provide particular kinds of support at repeated points of time may not effectively capture ties that are active but whose roles have changed. This article shows that a significant minority of network members change the kinds of support they provide. They either discontinue a support previously provided or provide a new type of support. We examine the implications of this finding for longitudinal studies of support networks based on single name generators and show that this practice can result in frequent misperceptions of network membership change.