Data Sharing on Untrusted Storage with Attribute-Based Encryption

Storing data on untrusted storage makes secure data sharing a challenge issue. On one hand, data access policies should be enforced on these storage servers; on the other hand, confidentiality of sensitive data should be well protected against them. Cryptographic methods are usually applied to address this issue -- only encrypted data are stored on storage servers while retaining secret key(s) to the data owner herself; user access is granted by issuing the corresponding data decryption keys. The main challenges for cryptographic methods include simultaneously achieving system scalability and fine-grained data access control, efficient key/user management, user accountability and etc. To address these challenge issues, this dissertation studies and enhances a novel public-key cryptography -- attribute-based encryption (ABE), and applies it for fine-grained data access control on untrusted storage. The first part of this dissertation discusses the necessity of applying ABE to secure data sharing on untrusted storage and addresses several security issues for ABE. More specifically, we propose three enhancement schemes for ABE: In the first enhancement scheme, we focus on how to revoke users in ABE with the help of untrusted servers. In this work, we enable the data owner to delegate most computation-intensive tasks pertained to user revocation to untrusted servers without disclosing data content to them. In the second enhancement scheme, we address key abuse attacks in ABE, in which authorized but malicious users abuse their access privileges by sharing their decryption keys with unauthorized users. Our proposed scheme makes it possible for the data owner to efficiently disclose the original key owner\u27s identity merely by checking the input and output of a suspicious user\u27s decryption device. Our third enhancement schemes study the issue of privacy preservation in ABE. Specifically, our proposed schemes hide the data owner\u27s access policy not only to the untrusted servers but also to all the users. The second part presents our ABE-based secure data sharing solutions for two specific applications -- Cloud Computing and Wireless Sensor Networks (WSNs). In Cloud Computing cloud servers are usually operated by third-party providers, which are almost certain to be outside the trust domain of cloud users. To secure data storage and sharing for cloud users, our proposed scheme lets the data owner (also a cloud user) generate her own ABE keys for data encryption and take the full control on key distribution/revocation. The main challenge in this work is to make the computation load affordable to the data owner and data consumers (both are cloud users). We address this challenge by uniquely combining various computation delegation techniques with ABE and allow both the data owner and data consumers to securely mitigate most computation-intensive tasks to cloud servers which are envisaged to have unlimited resources. In WSNs, wireless sensor nodes are often unattendedly deployed in the field and vulnerable to strong attacks such as memory breach. For securing storage and sharing of data on distributed storage sensor nodes while retaining data confidentiality, sensor nodes encrypt their collected data using ABE public keys and store encrypted data on storage nodes. Authorized users are given corresponding decryption keys to read data. The main challenge in this case is that sensor nodes are extremely resource-constrained and can just afford limited computation/communication load. Taking this into account we divide the lifetime of sensor nodes into phases and distribute the computation tasks into each phase. We also revised the original ABE scheme to make the overhead pertained to user revocation minimal for sensor nodes. Feasibility of the scheme is demonstrated by experiments on real sensor platforms

Talk up front:The influence of language matters on international military missions with a particular focus on the cooperation between soldiers and interpreters

Public Summary Talk Up Front The Influence of Language Matters on International Military Missions with a Particular Focus on the Cooperation between Soldiers and Interpreters Andrea van Dijk How do language issues affect military operations, and how in particular do soldiers and interpreters cooperate in mission areas to overcome such issues? This explorative study aims to enhance the understanding of the effects of the language barrier on international military cooperation. For that purpose, a predominantly sociological approach is adopted to investigate the dynamics at both the macro/meso-, and the micro-level of this specific form of interaction. The findings extensively demonstrate that language issues influence cooperation between international military personnel as well as collaboration with the local population. With regard to the latter, the linguistic and cultural skills of interpreters are crucial as they enable these agents to act as intermediaries between soldiers and local actors. Since modern military interventions typically encompass the deployment of servicemen among the population in conflict-harassed societies, effective cooperation between soldiers and interpreters is pivotal for the conduct of operations. Therefore, this research particularly focuses on this aspect of language matters in international military missions. Talk Up Front concludes that despite their vital role and position, smooth cooperation between soldiers and interpreters is not a matter of course. Efficient cooperative relationships typically do not emerge as a consequence of the military organization’s standard procedures, but have shown to strongly depend on individual traits. Particularly those soldiers and interpreters who can bridge the language gap and establish a constructive cooperation are instrumental to achieve mission success. These findings are based on, among others, 70 interviews with military personnel, national as well as local interpreters, and field work in Afghanistan. Ultimately, the study recommends that it is time for military organizations to acknowledge the presented insights and start learning for future operations

The Papers of Henry Clay. Volume 10. Candidate, Compromiser, Elder Statesman. January 1, 1844-June 29, 1852

The culminating volume in The Papers of Henry Clay begins in 1844, the year when Clay came within a hair\u27s breadth of achieving his lifelong goal-the presidency of the United States. Volume 10 of Clay\u27s papers, then, more than any other, reveals the Great Compromiser as a major player on the national political stage. Here are both the peak of his career and the inevitable decline. On a tour through the southern states in the spring of 1844, Clay seemed certain of gaining the Whig nomination and the national election, until a series of highly publicized letters opposing the annexation of Texas cost him crucial support in both South and North. In addition to the Texas issue, the bitter election was marked by a revival of charges of a corrupt bargain, the rise of nativism, the influence of abolitionism, and voter fraud. Democrat James K. Polk defeated Clay by a mere 38,000 popular votes, partly because of illegal ballots cast in New York City. Speaking out against the Mexican War, in which his favorite son was a casualty, the Kentuckian announced his willingness to accept the 1848 Whig nomination. But some of his closest political friends, including many Kentucky Whig leaders, believed he was unelectable and successfully supported war hero Zachary Taylor. The disconsolate Clay felt his public career was finally finished. Yet when a crisis erupted over the extension of slavery into the territories acquired from Mexico, he answered the call and returned to the United States Senate. There he introduced a series of resolutions that ultimately passed as the Compromise of 1850, the most famous of his three compromises. Clay\u27s last years were troubled ones personally, yet he remained in the Senate until his death in 1852, continuing to warn against sectional extremism and to stress the importance of the Union-messages that went unheeded as the nation Clay had served so well moved inexorably toward separation and civil war. Publication of this book is being assisted by a grant from the National Historical Publications and Records Commission. Melba Porter Hay is a specialist in the history of Kentucky and was associate editor of volumes 8 and 9 of The Papers of Henry Clay.https://uknowledge.uky.edu/upk_political_science_papers/1011/thumbnail.jp