Private Editing Using Untrusted Cloud Services

Abstract. We present a flexible approach for achieving user-controlled privacy and integrity of documents that are collaboratively authored within web-based document-editing applications. In this setting, the goal is to provide security without modifying the web application's client-side or server-side components. Instead, communication between both components is transparently intercepted and processed (if necessary) by means of a local proxy or browser plugin. We improve upon existing solutions by securely preserving real-time collaboration for encrypted documents and facilitating self-containment of the metadata (an overhead of encryption) within the same document. An architectural generalization is also presented that permits generic transformations and fine-grained access control. Security is assessed with respect to several threat models, and performance is evaluated alongside other approaches.

Section: Methodsmentioning

confidence: 99%

Section: Performancementioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

“…An improved solution appears in a more recent work by Huang and Evans [8]. The authors also develop a Firefox extension to transparently mediate Google Docs traffic.…”

Section: Related Workmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Privacy Supporting Cloud Computing: ConfiChair, a Case Study

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Ryan

2012

Abstract. Cloud computing means entrusting data to information systems that are managed by external parties on remote servers, in the "cloud", raising new privacy and confidentiality concerns. We propose a general technique for designing cloud services that allows the cloud to see only encrypted data, while still allowing it to perform data-dependent computations. The technique is based on key translations and mixes in web browsers.We focus on the particular cloud computing application of conference management. We identify the specific security and privacy risks that existing systems like EasyChair and EDAS pose, and address them with a protocol underlying ConfiChair, a novel cloud-based conference management system that offers strong security and privacy guarantees.In ConfiChair, authors, reviewers, and the conference chair interact through their browsers with the cloud, to perform the usual tasks of uploading and downloading papers and reviews. In contrast with current systems, in ConfiChair the cloud provider does not have access to the content of papers and reviews and the scores given by reviewers, and moreover is unable to link authors with reviewers of their paper.We express the ConfiChair protocol and its properties in the language of ProVerif, and prove that it does provide the intended properties.

Secure Quasi-Realtime Collaborative Editing over Low-Cost Storage Services

Zhang

Jin

Chang

et al. 2012

Abstract.A realtime collaborative editor facilitates concurrent editing of a document by multiple authors. It is desired that the document be shared only among the authors, and protected from the potentially curious server. Existing approaches have taken two distinct paths -centralized server based approaches that achieve high concurrency and meet real-time requirement but compromise on security and incur high server cost, and peer-to-peer based approaches that support security but compromise on users' convenience and mobility. In this paper, we observe that by relaxing the realtime requirement, we can achieve security, reduce server cost and yet exploit the conveniences of the centralized setting. In particular, we consider generic low-cost storage servers in the cloud that provide storage integrity but do not guarantee low-latency. Essentially, our method breaks the document into small encrypted regions that are stored on the server and coordinates the authors' access. Although two authors are unable to concurrently modify a same region, the system is able to provide "quasi-realtime" experience. By relaxing the requirement to quasi-realtime, the difficulties in achieving document consistency, and the requirement on resources are significantly reduced. We give a proof-of-concept implementation on top of Dropbox, a commercial cloud storage service. Preliminary user studies show that the system is effective.