Proceedings of the 17th ACM conference on Computer and communications security - CCS '10, 2010
Cloud computing, as an emerging computing paradigm, enables users to remotely store their data in... more Cloud computing, as an emerging computing paradigm, enables users to remotely store their data into a cloud so as to enjoy scalable services on-demand. Especially for small and medium-sized enterprises with limited budgets, they can achieve cost savings and productivity enhancements by using cloud-based services to manage projects, to make collaborations, and the like. However, allowing cloud service providers (CSPs), which are not in the same trusted domains as enterprise users, to take care of confidential data, may raise potential security and privacy issues. To keep the sensitive user data confidential against untrusted CSPs, a natural way is to apply cryptographic approaches, by disclosing decryption keys only to authorized users. However, when enterprise users outsource confidential data for sharing on cloud servers, the adopted encryption system should not only support fine-grained access control, but also provide high performance, full delegation, and scalability, so as to best serve the needs of accessing data anytime and anywhere, delegating within enterprises, and achieving a dynamic set of users. In this paper, we propose a scheme to help enterprises to efficiently share confidential data on cloud servers. We achieve this goal by first combining the hierarchical identity-based encryption (HIBE) system and the ciphertext-policy attribute-based encryption (CP-ABE) system, and then making a performance-expressivity tradeoff, finally applying proxy re-encryption and lazy re-encryption to our scheme.
The proliferation of the Internet computing and mobile computing technologies gives rise to the g... more The proliferation of the Internet computing and mobile computing technologies gives rise to the growth of mobile Internet applications. There are increasing demands on secure multicast services in the mobile Internet environment. An important issue in secure group communication is key management, which is concerned with distributing and updating the keys for encrypting the multicast messages in a group of mobile users. The challenges in designing secure and scalable key management protocols are dynamic updates of the key caused by frequent moves, joining and leaving of group members and the large size of a group for mobile Internet applications. In this paper, we propose a scalable and hierarchical key management (SHKM) protocol in the mobile Internet. In order to address the scalability issue, SHKM divides the group of users into different subgroups, where each subgroup uses its own key. Different from existing decentralized schemes, the subgroups in the SHKM protocol are organized into a hierarchical structure with different priorities. Each pair of parent-child subgroups is given a related factor based on their subgroup keys. The trusted third-party authority is responsible for computing the parameters. Based on these and some public parameters, users belonging to a higher-priority subgroup have the right and are capable to deduce the keys of lower-priority subgroups but the reverse operation is not allowed. Because the subgroup itself can perform the derivation, the number of re-keying messages for updating the global key management system across the subgroup boundaries can be significantly reduced. We compare the proposed protocol with some existing protocols, and conclude that the number of re-keying messages in our proposed protocol is the least among all these protocols.
IEEE Transactions on Parallel and Distributed Systems, 2014
Cloud computing as an emerging technology trend is expected to reshape the advances in informatio... more Cloud computing as an emerging technology trend is expected to reshape the advances in information technology. In a costefficient cloud environment, a user can tolerate a certain degree of delay while retrieving information from the cloud to reduce costs. In this paper, we address two fundamental issues in such an environment: privacy and efficiency. We first review a private keyword-based file retrieval scheme that was originally proposed by Ostrovsky. Their scheme allows a user to retrieve files of interest from an untrusted server without leaking any information. The main drawback is that it will cause a heavy querying overhead incurred on the cloud, and thus goes against the original intention of cost efficiency. In this paper, we present a scheme, termed efficient information retrieval for ranked query (EIRQ), based on an aggregation and distribution layer (ADL), to reduce querying overhead incurred on the cloud. In EIRQ, queries are classified into multiple ranks, where a higher ranked query can retrieve a higher percentage of matched files. A user can retrieve files on demand by choosing queries of different ranks. This feature is useful when there are a large number of matched files, but the user only needs a small subset of them. Under different parameter settings, extensive evaluations have been conducted on both analytical models and on a real cloud environment, in order to examine the effectiveness of our schemes.
The anti-spoofing community has been intensively proposing new methods for defending against new ... more The anti-spoofing community has been intensively proposing new methods for defending against new web-spoofing techniques. In this paper, we analyze the problems within current anti-spoofing mechanisms, and propose a new SSL protected trust model. Then, we describe the attacks on SSL protected trusted communication. In this paper, we also propose the new Automatic Detecting Security Indicator scheme (ADSI) to defend against spoofing attacks on SSL protected web servers. In a secure transaction, ADSI will randomly choose a picture and embed it into the current web browser at a random place. This can be triggered by any security relevant event that has occurred on the browser, and then automatic checking will be performed on the current active security status. When a mismatch of embedded pictures is detected, an alarm goes off to alert the users. Since an adversary is hard to replace or mimic the randomly embedded picture, the web-spoofing attack can not be mounted easily. In comparison with existing schemes, (1) the proposed scheme has the weakest security assumption, and places a very low burden on the user by automating the process of detection and recognition of web-spoofing for SSL-enabled trusted communication; (2) it has little intrusiveness on the browser; and (3) it can be implemented in a trusted PC at an Internet Cafe.
2009 IEEE 6th International Conference on Mobile Adhoc and Sensor Systems, 2009
The primary goal of the secure socket layer protocol (SSL) is to provide confidentiality and data... more The primary goal of the secure socket layer protocol (SSL) is to provide confidentiality and data integrity between two communicating entities. Since the most computationally expensive step in the SSL handshake protocol is the server's RSA decryption, it is introduced that the proposed secret exchange algorithm can be used to speedup SSL session initialization. The optimization strategy, which is based on the constrained model considering the user's requirements for Quality of Service (QoS), such as security ranking, focuses on the optimal result in different public key size. It is also introduced that the parameter is optimized when integrating user's requirements for Internet QoS such as the stability of the system and the tolerable response time. Finally, the proposed algorithm is evaluated to be practical and efficient through both analysis and simulation studies. Index Terms-Quality of Service (QoS), SSL handshake, optimization strategy, security ranking, tolerable response time I.
2009 International Conference on Computational Science and Engineering, 2009
A user stores his personal files in a cloud, and retrieves them wherever and whenever he wants. F... more A user stores his personal files in a cloud, and retrieves them wherever and whenever he wants. For the sake of protecting the user data privacy and the user queries privacy, a user should store his personal files in an encrypted form in a cloud, and then sends queries in the form of encrypted keywords. However, a simple encryption scheme may not work well when a user wants to retrieve only files containing certain keywords using a thin client. First, the user needs to encrypt and decrypt files frequently, which depletes too much CPU capability and memory power of the client. Second, the service provider couldn't determine which files contain keywords specified by a user if the encryption is not searchable. Therefore, it can only return back all the encrypted files. A thin client generally has limited bandwidth, CPU and memory, and this may not be a feasible solution under the circumstances. In this paper, we investigate the characteristics of cloud computing and propose an efficient privacy preserving keyword search scheme in cloud computing. It allows a service provider to participate in partial decipherment to reduce a client's computational overhead, and enables the service provider to search the keywords on encrypted files to protect the user data privacy and the user queries privacy efficiently. By proof, our scheme is semantically secure.
2010 10th IEEE International Conference on Computer and Information Technology, 2010
Over the past years, location-based routing protocols have been studied extensively in mobile ad ... more Over the past years, location-based routing protocols have been studied extensively in mobile ad hoc networks (MANETs). However, how to efficiently provide the location information for nodes is still a challenge. So far, many protocols have been proposed to solve this problem, most of which offer exact routing location information, and are complicated to implement in practice. In this paper, we propose a fuzzy location service (FLS), which introduces fuzzy location information. In FLS, a network is divided into hexagon cells. A node regards the center of the cell where it resides as its own fuzzy location. A node's location is not updated unless it moves into or out of a cell. This method is efficient and simple to implement. The simulation results show that FLS has better performance than GLS and HLS, in terms of routing waiting time and routing success ratio.
In the real world, companies would publish social networks to a third party, e.g., a cloud servic... more In the real world, companies would publish social networks to a third party, e.g., a cloud service provider, for marketing reasons. Preserving privacy when publishing social network data becomes an important issue. In this paper, we identify a novel type of privacy attack, termed 1*-neighborhood attack. We assume that an attacker has knowledge about the degrees of a target's one-hop neighbors, in addition to the target's 1-neighborhood graph, which consists of the one-hop neighbors of the target and the relationships among these neighbors. With this information, an attacker may re-identify the target from a k-anonymity social network with a probability higher than 1/k, where any node's 1-neighborhood graph is isomorphic with k − 1 other nodes' graphs. To resist the 1*-neighborhood attack, we define a key privacy property, probability indistinguishability, for an outsourced social network, and propose a heuristic indistinguishable group anonymization (HIGA) scheme to generate an anonymized social network with this privacy property. The empirical study indicates that the anonymized social networks can still be used to answer aggregate queries with high accuracy.
Behavior patterns of users in mobile social cloud are always based on real world relationships an... more Behavior patterns of users in mobile social cloud are always based on real world relationships and can be used to infer a level of trust between users. In this paper, we describe the implicit call behavioral graph which is formed by users' interactions with call. We rate these relationships to form a dynamic local cloud trust, which enables users to evaluate the trust values between users within the context of a mobile social cloud network. We, then, calculate local trust values according to users' behavioral attributes, such as call frequency, relevance, call moment, and satisfaction. Due to the unique nature of the social cloud, we discuss the propagation and aggregation of local trust values for global social cloud network. Finally, we evaluate the performance of our trust model through simulations, and show simulation results that demonstrate the importance of interaction-based behavioural relationships in recommendation system.
h i g h l i g h t s • A hierarchical trust model for MSNs based on cluster-group structure is pre... more h i g h l i g h t s • A hierarchical trust model for MSNs based on cluster-group structure is presented. • We construct an implicit social behavioral graph to describe trust relationships. • To extract the actual communities, a novel clustering algorithm is proposed. • We evaluate intragroup trust values using the hierarchical trust model for MSNs. • Trust values are aggregated and propagated based on intragroup trust values.
2011 IEEE Global Telecommunications Conference - GLOBECOM 2011, 2011
A key approach to secure cloud computing is for the data owner to store encrypted data in the clo... more A key approach to secure cloud computing is for the data owner to store encrypted data in the cloud, and issue decryption keys to authorized users. Then, when a user is revoked, the data owner will issue re-encryption commands to the cloud to re-encrypt the data, to prevent the revoked user from decrypting the data, and to generate new decryption keys to valid users, so that they can continue to access the data. However, since a cloud computing environment is comprised of many cloud servers, such commands may not be received and executed by all of the cloud servers due to unreliable network communications. In this paper, we solve this problem by proposing a timebased re-encryption scheme, which enables the cloud servers to automatically re-encrypt data based on their internal clocks. Our solution is built on top of a new encryption scheme, attributebased encryption, to allow fine-grain access control, and does not require perfect clock synchronization for correctness.
2012 Second International Conference on Cloud and Green Computing, 2012
Cloud computing has emerged as a new type of commercial paradigm. As a typical cloud service, eac... more Cloud computing has emerged as a new type of commercial paradigm. As a typical cloud service, each file stored in the cloud is described with several keywords. By querying the cloud with certain keywords, a user can retrieve files whose keywords match his query. An organization that has thousands of users querying the cloud can set multiple proxy servers inside itself to reduce the querying cost. All users can be classified into different groups, and the users in a group will send their queries to the same proxy server, which will query the cloud with a combined query, i.e., the union of keywords in a group of queries. In such an environment, an important problem is cost efficiency, i.e., how to classify users into different groups so that the total number of returned files is minimized. Observing that this is mainly affected by the number of keywords in the combined queries, our problem is translated to classifying n users into k groups in the case of k proxy servers, so that the number of keywords in k combined queries is minimized. Since more common keywords in a group of queries will generate less keywords in the combined queries, we should group users with the most common keywords together. Two additional aspects needed to be addressed are load balancing and robustness, i.e., the workloads among proxy servers are balanced and each user obtains search results even if some proxy servers fail. To solve above problems simultaneously, we propose mathematic grouping and heuristic grouping strategies, where mathematic grouping solves the relaxed problem by using a local optimization method, and heuristic grouping is based on the classical heuristic clustering algorithm, K-means. Extensive evaluations have been conducted on the analytical model to verify the effectiveness of our strategies.
International Conference on Parallel Processing, 2004. ICPP 2004., 2004
We propose a membership protocol for group communications in mobile Internet. The protocol is cal... more We propose a membership protocol for group communications in mobile Internet. The protocol is called RGB, which is the acronym of "a Ring-based hierarchy of access proxies, access Gateways, and Border routers". RGB runs in a parallel and distributed way in the sense that each network entity in the ring-based hierarchy maintains local information about its possible leader, previous, next, parent and child neighbors, and that each network entity independently collects/generates membership change information, which is propagated by the one-round membership algorithm concurrently running in all the logical rings. We prove that the proposed protocol is scalable in the sense that the scalability of a ring-based hierarchy is as good as that of a tree-based hierarchy. We also prove that the proposed protocol is reliable, in the sense that, with high probability of 99.500%, a ring-based hierarchy with up to 1000 access proxies attached by a large number of mobile hosts will not partition when node faulty probability is bounded by 0.1%; if at most 3 partitions are allowed, then the Function-Well probability of the hierarchy is 99.999% accordingly.
Cloud computing as an emerging technology trend is expected to reshape the advances in informatio... more Cloud computing as an emerging technology trend is expected to reshape the advances in information technology. In this paper, we address two fundamental issues in a cloud environment: privacy and efficiency. We first review a private keyword-based file retrieval scheme proposed by Ostrovsky et. al. Then, based on an aggregation and distribution layer (ADL), we present a scheme, termed efficient information retrieval for ranked query (EIRQ), to further reduce querying costs incurred in the cloud. Queries are classified into multiple ranks, where a higher ranked query can retrieve a higher percentage of matched files. Extensive evaluations have been conducted on an analytical model to examine the effectiveness of our scheme.
Pervasive computing, or ubiquitous computing, has evolved into an active research area, as a resu... more Pervasive computing, or ubiquitous computing, has evolved into an active research area, as a result of the tremendous advances in a broad range of technologies, including wireless networking, mobile and distributed computing, sensor systems, RFID technology, etc. Pervasive computing, which enables users to obtain information and services anytime and anywhere, could have a wide range of applications, such as healthcare, homecare, intelligent transportation, and environmental monitoring. However, it is quite difficult for pervasive applications to satisfy trust, security and privacy requirements, due to their ability to gather sensitive information and change the environment via actuating devices autonomously. This special section aims at presenting a collection of high quality research papers that report the latest research achievements in trust, security and privacy for pervasive applications, and providing a forum to present and discuss emerging ideas and trends in this highly challenging field. In this special section, we selected 8 papers out of 37 total submissions, which demonstrate some novel works in this field. A detailed overview of the selected works is given below. The first paper, "A Holistic Approach Examining RFID Design for Security and Privacy," [1] presents a holistic approach to ensure security and privacy for Radio
The primary goal of the secure socket layer protocol (SSL) is to provide confidentiality and data... more The primary goal of the secure socket layer protocol (SSL) is to provide confidentiality and data integrity between two communicating entities. Since the most computationally expensive step in the SSL handshake protocol is the server's RSA decryption, it is introduced that the proposed secret exchange algorithm can be used to speed up the SSL session initialization. This paper first points out that the previous batch method is impractical since it requires multiple certificates. It then proposes a unique certificate scheme to overcome the problem. The optimization strategy, which is based on the constrained model considering the user requirements-aware security ranking, focuses on the optimal result in different public key sizes. It is also introduced that the parameter is optimized when integrating user requirements for Internet QoS, such as the stability of the system and the tolerable response time. Finally, the proposed algorithm is evaluated to be practical and efficient through both analysis and simulation studies.
Journal of Parallel and Distributed Computing, 2012
Network security and privacy Network security and privacy Network security and privacy Network se... more Network security and privacy Network security and privacy Network security and privacy Network security and privacy Social networks and cloud computing Social networks and cloud computing Social networks and cloud computing Social networks and cloud computing • Internet (NSF GENI) • Mesh networks (NSF MRI) • Sensor networks (NSF NeTS) • Delay-tolerant networks (NSF TC) • Underwater networks (Navy Yard) • Vehicular networks (SEPTA Regional Rail) • Wireless networks (ARO) • RFID and medical applications (PA)
Journal of Network and Computer Applications, 2012
Cloud storage services enable users to remotely access data in a cloud anytime and anywhere, usin... more Cloud storage services enable users to remotely access data in a cloud anytime and anywhere, using any device, in a pay-as-you-go manner. Moving data into a cloud offers great convenience to users since they do not have to care about the large capital investment in both the deployment and management of the hardware infrastructures. However, allowing a cloud service provider (CSP), whose purpose is mainly for making a profit, to take the custody of sensitive data, raises underlying security and privacy issues. To keep user data confidential against an untrusted CSP, a natural way is to apply cryptographic approaches, by disclosing the data decryption key only to authorized users. However, when a user wants to retrieve files containing certain keywords using a thin client, the adopted encryption system should not only support keyword searching over encrypted data, but also provide high performance. In this paper, we investigate the characteristics of cloud storage services and propose a secure and privacy preserving keyword searching (SPKS) scheme, which allows the CSP to participate in the decipherment, and to return only files containing certain keywords specified by the users, so as to reduce both the computational and communication overhead in decryption for users, on the condition of preserving user data privacy and user querying privacy. Performance analysis shows that the SPKS scheme is applicable to a cloud environment.
International Journal of Ad Hoc and Ubiquitous Computing, 2009
This paper describes a secure multicast infrastructure for large-scale group communications in Mo... more This paper describes a secure multicast infrastructure for large-scale group communications in Mobile Internet and proposes a key management protocol based on the infrastructure. The multicast communication domain is logically divided into several administrative areas with a key server associated with each area. All the key servers participate in a Public Key Infrastructure (PKI) as trusted entities known by the subgroup members. Therefore, it's efficient to minimize the re-key overhead implemented in the mobile host tier. The simulation results show that the proposed protocol has better performance compared to the centralized protocols without PKI support. The numbers of the real re-key messages and the re-key events are reduced to approximately 30% and 65%, respectively.
A fundamental approach for secure data sharing in a cloud environment is to let the data owner en... more A fundamental approach for secure data sharing in a cloud environment is to let the data owner encrypt data before outsouring. To simultaneously achieve fine-grained access control on encrypted data and scalable user revocation, existing work combines attribute-based encryption (ABE) and proxy re-encryption (PRE) to delegate the cloud service provider (CSP) to execute re-encryption. However, the data owner should be online in order to send the PRE keys to the CSP in a timely fashion, to prevent the revoked user from accessing the future data. The delay of issuing the PRE keys may cause potential security risks. In this paper, we propose a time-based proxy re-encryption (TimePRE) scheme to allow a user's access right to expire automatically after a predetermined period of time. In this case, the data owner can be offline in the process of user revocations. The basic idea is to incorporate the concept of time into the combination of ABE and PRE. Specifically, each data is associated with an attribute-based access structure and an access time, and each user is identified by a set of attributes and a set of eligible time periods which denote the period of validity of the user's access right. Then, the data owner and the CSP are required to share a root secret key in advance, with which CSP can automatically update the access time of the data with the time that it receives a data access request. Therefore,
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Papers by Guojun Wang