With the increasing importance of images in people’s daily life, content-based image retrieval (CBIR) has been widely studied. Compared with text documents, images consume much more storage space. Hence, its maintenance is considered to be a typical example for cloud storage outsourcing. For privacy-preserving purposes, sensitive images, such as medical and personal images, need to be encrypted before outsourcing, which makes the CBIR technologies in plaintext domain to be unusable. In this paper, we propose a scheme that supports CBIR over encrypted images without leaking the sensitive information to the cloud server. First, feature vectors are extracted to represent the corresponding images. After that, the pre-filter tables are constructed by locality-sensitive hashing to increase search efficiency. Moreover, the feature vectors are protected by the secure kNN algorithm, and image pixels are encrypted by a standard stream cipher. In addition, considering the case that the authorized query users may illegally copy and distribute the retrieved images to someone unauthorized, we propose a watermark-based protocol to deter such illegal distributions. In our watermark-based protocol, a unique watermark is directly embedded into the encrypted images by the cloud server before images are sent to the query user. Hence, when image copy is found, the unlawful query user who distributed the image can be traced by the watermark extraction. The security analysis and the experiments show the security and efficiency of the proposed scheme.

A Privacy-Preserving and Copy-Deterrence Content-Based Image Retrieval Scheme in Cloud Computing

Business processes automation requires the specification of process structures as well as the definition of resources involved in the execution of these processes. While the modeling of business processes and workflows is well researched, the link between the organizational elements and process activities is less well understood, and current developments in the web services choreography area completely neglect the organizational aspect of workflow applications. The purpose of this paper is to give an overview of the organizational aspects of workflow technology in the context of the workflow life cycle, to provide a review of existing work, and to develop guidelines for the design of a workflow-enabled organization, which can be used by both workflow vendors and users.

Organizational Management in Workflow Applications – Issues and Perspectives

EPCBIR: An efficient and privacy-preserving content-based image retrieval scheme in cloud computing

Geo-replicated storage systems are at the core of current Internet services. The designers of the replication protocols used by these systems must choose between either supporting low-latency, eventually-consistent operations, or ensuring strong consistency to ease application correctness. We propose an alternative consistency model, Explicit Consistency, that strengthens eventual consistency with a guarantee to preserve specific invariants defined by the applications. Given these application-specific invariants, a system that supports Explicit Consistency identifies which operations would be unsafe under concurrent execution, and allows programmers to select either violation-avoidance or invariant-repair techniques. We show how to achieve the former, while allowing operations to complete locally in the common case, by relying on a reservation system that moves coordination off the critical path of operation execution. The latter, in turn, allows operations to execute without restriction, and restore invariants by applying a repair operation to the database state. We present the design and evaluation of Indigo, a middleware that provides Explicit Consistency on top of a causally-consistent data store. Indigo guarantees strong application invariants while providing similar latency to an eventually-consistent system in the common case.

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Putting consistency back into eventual consistency

Architecture for a scalable, pluggable multi-party, and distributed multimedia conferencing. A centralized policy and control conferencing component allows the seamless plug-in of different distributed media components (e.g., data, audio/video, messaging) to accommodate client participation in a conference session. The centralized conference control component includes the following: a conference notification service for accepting subscriptions to the conference state and notifying subscribers about changes to that state; a conference policy and roster control service for storing and manipulating conference policy and rosters; a security service for user authorization/authentication based on user identity information; a scheduling service for conference scheduling; an allocation service for allocating the most available media component(s) for a conference session; and, an MCU management service for conference policy and roster management of the distributed media components.

Distributable, scalable, pluggable conferencing architecture

Storage requirements for visual data have been increasing in recent years, following the emergence of many highly interactive multimedia services and applications for mobile devices in both personal and corporate scenarios. This has been a key driving factor for the adoption of cloud-based data outsourcing solutions. However, outsourcing data storage to the Cloud also leads to new security challenges that must be carefully addressed, especially regarding privacy. In this paper we propose a secure framework for outsourced privacy-preserving storage and retrieval in large shared image repositories. Our proposal is based on IES-CBIR, a novel Image Encryption Scheme that exhibits Content-Based Image Retrieval properties. The framework enables both encrypted storage and searching using Content-Based Image Retrieval queries while preserving privacy against honest-but-curious cloud administrators. We have built a prototype of the proposed framework, formally analyzed and proven its security properties, and experimentally evaluated its performance and retrieval precision. Our results show that IES-CBIR is provably secure, allows more efficient operations than existing proposals, both in terms of time and space complexity, and paves the way for new practical application scenarios.

Practical Privacy-Preserving Content-Based Retrieval in Cloud Image Repositories

In asynchronous collaborative applications, users usually collaborate accessing and modifying shared information independently. We have designed and implemented a replicated object store to support such applications in distributed environments that include mobile computers. Unlike most data management systems, awareness support is integrated in the system. To improve the chance for new contributions, the system provides high data availability. The development of applications is supported by an object framework that decomposes objects in several components, each one managing a different aspect of object "execution". New data types may be created relying on pre-defined components to handle concurrent updates, awareness information, etc.

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Data management support for asynchronous groupware

Storage requirements for visual data have been increasing in recent years, following the emergence of many new highly interactive multimedia services and applications for both personal and corporate use. This has been a key driving factor for the adoption of cloud-based data outsourcing solutions. However, outsourcing data storage to the Cloud also leads to new challenges that must be carefully addressed, especially regarding privacy. In this paper we propose a secure framework for outsourced privacy-preserving storage and retrieval in large image repositories. Our proposal is based on IES-CBIR, a novel Image Encryption Scheme that displays Content-Based Image Retrieval properties. Our solution enables both encrypted storage and searching using CBIR queries while preserving privacy. We have built a prototype of the proposed framework, formally analyzed and proven its security properties, and experimentally evaluated its performance and precision. Our results show that IES-CBIR is provably secure, allows more efficient operations than existing proposals, both in terms of time and space complexity, and enables more reliable practical application scenarios.

Privacy-Preserving Content-Based Image Retrieval in the Cloud

Mobile computing characteristics demand data management systems to support independent operation. However, the execution of updates in a mobile client usually need to be considered tentative because uncoordinated updates that conflict need to be reconciled. In this paper we present a mechanism to independently guarantee that updates can be executed in the server without conflicts. To this end, clients obtain leased reservations upon the database state. Updates are specified as common small PL/SQL programs, dubbed mobile transactions, that execute both in the mobile client and in the server. Using the available reservations, the client transparently verifies that a transaction can be executed in the same way both in the mobile client and in the server, thus leading to the same final result. Mobile transactions may specify conflict detection and resolution rules to be used when transactions cannot be locally guaranteed.

Reservations for Conflict Avoidance in a Mobile Database System

It is common that, in a long-term asynchronous collaborative activity, groups of users engage in occasional synchronous sessions. In this paper, we discuss the data management requirements for supporting this common work practice. As users interact in different ways in each setting, requirements and solutions often need to be different. We present a data management system that allows to integrate a synchronous session in the context of a long-term asynchronous interaction, using the suitable data sharing techniques in each setting and an automatic mechanism to convert the long sequence of small updates produced in a synchronous session into a large asynchronous contribution. We exemplify the use of our approach with two multi-synchronous applications.

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Henrique Domingos

Papers

Practical Privacy-Preserving Content-Based Retrieval in Cloud Image Repositories

Data management support for asynchronous groupware

Privacy-Preserving Content-Based Image Retrieval in the Cloud

Reservations for Conflict Avoidance in a Mobile Database System

Integrating synchronous and asynchronous interactions in groupware applications