A main challenge of attribute-based access control (ABAC) is the handling of missing information. Several studies show that the way standard ABAC mechanisms (e.g., XACML) handle missing information is flawed, making ABAC policies vulnerable to attribute-hiding attacks. Recent work addressed the problem of missing information in ABAC by introducing the notion of extended evaluation, where the evaluation of a query considers all possible ways of extending that query. This method counters attribute-hiding attacks, but a naive implementation is intractable, as it requires an evaluation of the whole query space. In this paper, we present an efficient extended ABAC evaluation method that relies on the encoding of ABAC policies as multiple Binary Decision Diagrams (BDDs), and on the specification of query constraints to avoid including the evaluation of queries that do not represent a valid state of the system. We illustrate our approach on two real-world case studies, which would be intractable with the original method and are analyzed in seconds with our method.
{"title":"Efficient Extended ABAC Evaluation","authors":"C. Morisset, T. Willemse, Nicola Zannone","doi":"10.1145/3205977.3205980","DOIUrl":"https://doi.org/10.1145/3205977.3205980","url":null,"abstract":"A main challenge of attribute-based access control (ABAC) is the handling of missing information. Several studies show that the way standard ABAC mechanisms (e.g., XACML) handle missing information is flawed, making ABAC policies vulnerable to attribute-hiding attacks. Recent work addressed the problem of missing information in ABAC by introducing the notion of extended evaluation, where the evaluation of a query considers all possible ways of extending that query. This method counters attribute-hiding attacks, but a naive implementation is intractable, as it requires an evaluation of the whole query space. In this paper, we present an efficient extended ABAC evaluation method that relies on the encoding of ABAC policies as multiple Binary Decision Diagrams (BDDs), and on the specification of query constraints to avoid including the evaluation of queries that do not represent a valid state of the system. We illustrate our approach on two real-world case studies, which would be intractable with the original method and are analyzed in seconds with our method.","PeriodicalId":423087,"journal":{"name":"Proceedings of the 23nd ACM on Symposium on Access Control Models and Technologies","volume":"2 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2018-06-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"134613097","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The Internet of Things (IoT) is receiving considerable attention from both industry and academia because of the new business models that it enables and the new security and privacy challenges that it generates. Major Cloud Service Providers (CSPs) have proposed platforms to support IoT by combining cloud and edge computing. However, the security mechanisms available in the cloud have been extended to IoT with some shortcomings with respect to the management and enforcement of access control policies. Access Control as a Service (ACaaS) is emerging as a solution to overcome these difficulties. The paper proposes a lazy approach to ACaaS that allows the specification and management of policies independently of the CSP while leveraging its enforcement mechanisms. We demonstrate the approach by investigating (also experimentally) alternative deployments in the IoT platform offered by Amazon Web Services on a realistic smart lock solution.
{"title":"A Lazy Approach to Access Control as a Service (ACaaS) for IoT: An AWS Case Study","authors":"Tahir Ahmad, Umberto Morelli, Silvio Ranise, Nicola Zannone","doi":"10.1145/3205977.3205989","DOIUrl":"https://doi.org/10.1145/3205977.3205989","url":null,"abstract":"The Internet of Things (IoT) is receiving considerable attention from both industry and academia because of the new business models that it enables and the new security and privacy challenges that it generates. Major Cloud Service Providers (CSPs) have proposed platforms to support IoT by combining cloud and edge computing. However, the security mechanisms available in the cloud have been extended to IoT with some shortcomings with respect to the management and enforcement of access control policies. Access Control as a Service (ACaaS) is emerging as a solution to overcome these difficulties. The paper proposes a lazy approach to ACaaS that allows the specification and management of policies independently of the CSP while leveraging its enforcement mechanisms. We demonstrate the approach by investigating (also experimentally) alternative deployments in the IoT platform offered by Amazon Web Services on a realistic smart lock solution.","PeriodicalId":423087,"journal":{"name":"Proceedings of the 23nd ACM on Symposium on Access Control Models and Technologies","volume":"21 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2018-06-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"134613213","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Lingjing Yu, Sri Mounica Motipalli, Dongwon Lee, Peng Liu, Heng Xu, Qingyun Liu, Jianlong Tan, Bo Luo
With the dramatically increasing participation in online social networks (OSNs), huge amount of private information becomes available on such sites. It is critical to preserve users' privacy without preventing them from socialization and sharing. Unfortunately, existing solutions fall short meeting such requirements. We argue that the key component of OSN privacy protection is protecting (sensitive) content -- privacy as having the ability to control information dissemination. We follow the concepts of private information boundaries and restricted access and limited control to introduce a social circle model. We articulate the formal constructs of this model and the desired properties for privacy protection in the model. We show that the social circle model is efficient yet practical, which provides certain level of privacy protection capabilities to users, while still facilitates socialization. We then utilize this model to analyze the most popular social network platforms on the Internet (Facebook, Google+, WeChat, etc), and demonstrate the potential privacy vulnerabilities in some social networks. Finally, we discuss the implications of the analysis, and possible future directions.
{"title":"My Friend Leaks My Privacy: Modeling and Analyzing Privacy in Social Networks","authors":"Lingjing Yu, Sri Mounica Motipalli, Dongwon Lee, Peng Liu, Heng Xu, Qingyun Liu, Jianlong Tan, Bo Luo","doi":"10.1145/3205977.3205981","DOIUrl":"https://doi.org/10.1145/3205977.3205981","url":null,"abstract":"With the dramatically increasing participation in online social networks (OSNs), huge amount of private information becomes available on such sites. It is critical to preserve users' privacy without preventing them from socialization and sharing. Unfortunately, existing solutions fall short meeting such requirements. We argue that the key component of OSN privacy protection is protecting (sensitive) content -- privacy as having the ability to control information dissemination. We follow the concepts of private information boundaries and restricted access and limited control to introduce a social circle model. We articulate the formal constructs of this model and the desired properties for privacy protection in the model. We show that the social circle model is efficient yet practical, which provides certain level of privacy protection capabilities to users, while still facilitates socialization. We then utilize this model to analyze the most popular social network platforms on the Internet (Facebook, Google+, WeChat, etc), and demonstrate the potential privacy vulnerabilities in some social networks. Finally, we discuss the implications of the analysis, and possible future directions.","PeriodicalId":423087,"journal":{"name":"Proceedings of the 23nd ACM on Symposium on Access Control Models and Technologies","volume":"15 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2018-06-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"126775370","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Multi-party access control is gaining attention and prominence within the community, as access control models and systems are faced with complex, jointly-owned and jointly-managed content. Traditional single-user approaches lack the richness and flexibility to accommodate these scenarios, resulting in undesired disclosure of sensitive data and resources. Moving forward fundamental work in this area is critical. In particular, as personal data amasses and algorithms for data mining improve, personally identifiable information is more readily inferred and the practical implications of privacy decisions are relatively opaque. This is true even at the individual level, but the parallel problem for jointly managed content involves the cross product of these complex outcomes. In this presentation, we discuss fundamental requirements of successful multi-party access control mechanisms and contextualize these concepts with respect to the state of the art. Based on this analysis, we identify open challenges and draw a roadmap for future work.
{"title":"Multi-Party Access Control: Requirements, State of the Art and Open Challenges","authors":"A. Squicciarini, S. Rajtmajer, Nicola Zannone","doi":"10.1145/3205977.3205999","DOIUrl":"https://doi.org/10.1145/3205977.3205999","url":null,"abstract":"Multi-party access control is gaining attention and prominence within the community, as access control models and systems are faced with complex, jointly-owned and jointly-managed content. Traditional single-user approaches lack the richness and flexibility to accommodate these scenarios, resulting in undesired disclosure of sensitive data and resources. Moving forward fundamental work in this area is critical. In particular, as personal data amasses and algorithms for data mining improve, personally identifiable information is more readily inferred and the practical implications of privacy decisions are relatively opaque. This is true even at the individual level, but the parallel problem for jointly managed content involves the cross product of these complex outcomes. In this presentation, we discuss fundamental requirements of successful multi-party access control mechanisms and contextualize these concepts with respect to the state of the art. Based on this analysis, we identify open challenges and draw a roadmap for future work.","PeriodicalId":423087,"journal":{"name":"Proceedings of the 23nd ACM on Symposium on Access Control Models and Technologies","volume":"114 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2018-06-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"132035515","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
R. D. Pietro, Xavier Salleras, Matteo Signorini, Erez Waisbard
One of the biggest challenges for the Internet of Things (IoT) is to bridge the currently fragmented trust domains. The traditional PKI model relies on a common root of trust and does not fit well with the heterogeneous IoT ecosystem where constrained devices belong to independent administrative domains. In this work we describe a distributed trust model for the IoT that leverages the existing trust domains and bridges them to create end-to-end trust between IoT devices without relying on any common root of trust. Furthermore we define a new cryptographic primitive, denoted as obligation chain designed as a credit-based Blockchain with a built-in reputation mechanism. Its innovative design enables a wide range of use cases and business models that are simply not possible with current Blockchain-based solutions while not experiencing traditional blockchain delays. We provide a security analysis for both the obligation chain and the overall architecture and provide experimental tests that show its viability and quality.
{"title":"A blockchain-based Trust System for the Internet of Things","authors":"R. D. Pietro, Xavier Salleras, Matteo Signorini, Erez Waisbard","doi":"10.1145/3205977.3205993","DOIUrl":"https://doi.org/10.1145/3205977.3205993","url":null,"abstract":"One of the biggest challenges for the Internet of Things (IoT) is to bridge the currently fragmented trust domains. The traditional PKI model relies on a common root of trust and does not fit well with the heterogeneous IoT ecosystem where constrained devices belong to independent administrative domains. In this work we describe a distributed trust model for the IoT that leverages the existing trust domains and bridges them to create end-to-end trust between IoT devices without relying on any common root of trust. Furthermore we define a new cryptographic primitive, denoted as obligation chain designed as a credit-based Blockchain with a built-in reputation mechanism. Its innovative design enables a wide range of use cases and business models that are simply not possible with current Blockchain-based solutions while not experiencing traditional blockchain delays. We provide a security analysis for both the obligation chain and the overall architecture and provide experimental tests that show its viability and quality.","PeriodicalId":423087,"journal":{"name":"Proceedings of the 23nd ACM on Symposium on Access Control Models and Technologies","volume":"222 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2018-06-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"130483060","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Bruhadeshwar Bezawada, S. Kulkarni, I. Ray, I. Ray, Ruiping Li
Broadcast authentication is an important problem in several network settings such as wireless sensor networks and ad-hoc networks. We focus on the problem of independent key distribution protocols, which use efficient symmetric key signatures in distributed systems to permit (local) broadcast authentication. We focus on five types of communication graphs: (1) star, (2) acyclic, (3) planar, (4) complete bipartite, and (5) fully connected graphs. A star graph is the simplest network topology where a central node is transmitting authenticated broadcast messages to several satellite nodes. For star graphs, we show that as n, the number of satellite nodes in the star network, tends to infinity, it suffices to maintain logn+1/2loglogn + 1 keys at the center node, but logn+1/2loglogn keys do not suffice. We establish that this is the optimal lower bound on the number of keys for a star graph. Building on this result, we describe storage efficient key distribution for acyclic, planar, and complete bipartite graphs, when compared to existing key distribution schemes. We extend our scheme for fully connected graphs and show that it is sufficient to store O(c log2 N) keys per node where c<1. We perform a detailed analysis of collusion resistance of our protocols and show the trade-offs against internal and external attacks depending on the size of storage. Finally, we demonstrate the practical applicability of our protocols for wireless sensor networks.
{"title":"Independent Key Distribution Protocols for Broadcast Authentication","authors":"Bruhadeshwar Bezawada, S. Kulkarni, I. Ray, I. Ray, Ruiping Li","doi":"10.1145/3205977.3205985","DOIUrl":"https://doi.org/10.1145/3205977.3205985","url":null,"abstract":"Broadcast authentication is an important problem in several network settings such as wireless sensor networks and ad-hoc networks. We focus on the problem of independent key distribution protocols, which use efficient symmetric key signatures in distributed systems to permit (local) broadcast authentication. We focus on five types of communication graphs: (1) star, (2) acyclic, (3) planar, (4) complete bipartite, and (5) fully connected graphs. A star graph is the simplest network topology where a central node is transmitting authenticated broadcast messages to several satellite nodes. For star graphs, we show that as n, the number of satellite nodes in the star network, tends to infinity, it suffices to maintain logn+1/2loglogn + 1 keys at the center node, but logn+1/2loglogn keys do not suffice. We establish that this is the optimal lower bound on the number of keys for a star graph. Building on this result, we describe storage efficient key distribution for acyclic, planar, and complete bipartite graphs, when compared to existing key distribution schemes. We extend our scheme for fully connected graphs and show that it is sufficient to store O(c log2 N) keys per node where c<1. We perform a detailed analysis of collusion resistance of our protocols and show the trade-offs against internal and external attacks depending on the size of storage. Finally, we demonstrate the practical applicability of our protocols for wireless sensor networks.","PeriodicalId":423087,"journal":{"name":"Proceedings of the 23nd ACM on Symposium on Access Control Models and Technologies","volume":"57 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2018-06-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"134060349","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Mining access control policies can reduce the burden of adopting more modern access control models by automating the process of generating policies based on existing authorization information in a system. Previous work in this area has focused on mining positive authorizations only. That includes the literature on mining role-based access control policies (which are naturally about positive authorization) and even more recent work on mining attribute-based access control (ABAC) policies. However, various theoretical access control models (including ABAC), specification standards (such as XACML), and implementations (such as operating systems and databases) support negative authorization as well as positive authorization. In this paper, we propose a novel approach to mine ABAC policies that may contain both positive and negative authorization rules. We evaluate our approach using two different policies in terms of correctness, quality of rules (conciseness), and time. We show that while achieving the new goal of supporting negative authorizations, our proposed algorithm outperforms existing approach to ABAC mining in terms of time.
{"title":"Mining Positive and Negative Attribute-Based Access Control Policy Rules","authors":"Padmavathi Iyer, A. Masoumzadeh","doi":"10.1145/3205977.3205988","DOIUrl":"https://doi.org/10.1145/3205977.3205988","url":null,"abstract":"Mining access control policies can reduce the burden of adopting more modern access control models by automating the process of generating policies based on existing authorization information in a system. Previous work in this area has focused on mining positive authorizations only. That includes the literature on mining role-based access control policies (which are naturally about positive authorization) and even more recent work on mining attribute-based access control (ABAC) policies. However, various theoretical access control models (including ABAC), specification standards (such as XACML), and implementations (such as operating systems and databases) support negative authorization as well as positive authorization. In this paper, we propose a novel approach to mine ABAC policies that may contain both positive and negative authorization rules. We evaluate our approach using two different policies in terms of correctness, quality of rules (conciseness), and time. We show that while achieving the new goal of supporting negative authorizations, our proposed algorithm outperforms existing approach to ABAC mining in terms of time.","PeriodicalId":423087,"journal":{"name":"Proceedings of the 23nd ACM on Symposium on Access Control Models and Technologies","volume":"195 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2018-06-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"129420742","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Lakshya Tandon, Philip W. L. Fong, R. Safavi-Naini
Permissions are highly sensitive in Internet-of-Things (IoT) applications, as IoT devices collect our personal data and control the safety of our environment. Rather than simply granting permissions, further constraints shall be imposed on permission usage so as to realize the Principle of Least Privilege. Since IoT devices are physically embedded, they are often accessed in a particular sequence based on their relative physical positions. Monitoring if such sequencing constraints are honoured when IoT devices are accessed provides a means to fence off malicious accesses. This paper proposes a history-based capability system, HCAP, for enforcing permission sequencing constraints in a distributed authorization environment. We formally establish the security guarantees of HCAP, and empirically evaluate its performance.
{"title":"HCAP: A History-Based Capability System for IoT Devices","authors":"Lakshya Tandon, Philip W. L. Fong, R. Safavi-Naini","doi":"10.1145/3205977.3205978","DOIUrl":"https://doi.org/10.1145/3205977.3205978","url":null,"abstract":"Permissions are highly sensitive in Internet-of-Things (IoT) applications, as IoT devices collect our personal data and control the safety of our environment. Rather than simply granting permissions, further constraints shall be imposed on permission usage so as to realize the Principle of Least Privilege. Since IoT devices are physically embedded, they are often accessed in a particular sequence based on their relative physical positions. Monitoring if such sequencing constraints are honoured when IoT devices are accessed provides a means to fence off malicious accesses. This paper proposes a history-based capability system, HCAP, for enforcing permission sequencing constraints in a distributed authorization environment. We formally establish the security guarantees of HCAP, and empirically evaluate its performance.","PeriodicalId":423087,"journal":{"name":"Proceedings of the 23nd ACM on Symposium on Access Control Models and Technologies","volume":"26 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2018-03-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"117005975","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
It is our great pleasure to welcome you to the ACM Symposium on Access Control Models and Technologies (SACMAT 2016), taking place in Shanghai, China, on June 6-8, 2016. This is the 21st edition of the symposium series, continuing the tradition of being the premier forum for presentation of research results and experience reports on leading edge issues of access control in terms of models, systems, applications, and theory. The symposium aims to share novel access control solutions that fulfill the needs of heterogeneous applications and environments, and to identify new directions for future research and development. SACMAT provides researchers and practitioners with a unique opportunity to share their perspectives with others interested in the various aspects of access control, aside from visiting the various attractions offered by the big international metropolis Shanghai. This year, 55 abstracts and papers were submitted from a variety of countries around the world. Submissions were anonymous; each paper has been reviewed by at least three reviewers who are experts in the field. Extensive online discussions took place to make the selections for the symposium. The program committee finally accepted 18 papers as full papers and 3 papers as short ones for presentation at the symposium. The topics covered include network and mobile access control, access control in applications, policy engineering, access control specification and access control enforcement. In addition to the main research paper sessions, the symposium offers a panel discussion session entitled "Security and privacy in the era of Internet of Things: research opportunities and challenges", and a poster session. Above all, the conference proudly presents three exciting keynote talks by Virgil Gligor of Carnegie Mellon University, Bhavani Thuraisingham of University of Texas at Dallas, and Robert Deng of Singapore Management University, respectively.
{"title":"Proceedings of the 23nd ACM on Symposium on Access Control Models and Technologies","authors":"X. S. Wang, Lujo Bauer, F. Kerschbaum","doi":"10.1145/3205977","DOIUrl":"https://doi.org/10.1145/3205977","url":null,"abstract":"It is our great pleasure to welcome you to the ACM Symposium on Access Control Models and Technologies (SACMAT 2016), taking place in Shanghai, China, on June 6-8, 2016. This is the 21st edition of the symposium series, continuing the tradition of being the premier forum for presentation of research results and experience reports on leading edge issues of access control in terms of models, systems, applications, and theory. The symposium aims to share novel access control solutions that fulfill the needs of heterogeneous applications and environments, and to identify new directions for future research and development. SACMAT provides researchers and practitioners with a unique opportunity to share their perspectives with others interested in the various aspects of access control, aside from visiting the various attractions offered by the big international metropolis Shanghai. \u0000 \u0000This year, 55 abstracts and papers were submitted from a variety of countries around the world. Submissions were anonymous; each paper has been reviewed by at least three reviewers who are experts in the field. Extensive online discussions took place to make the selections for the symposium. The program committee finally accepted 18 papers as full papers and 3 papers as short ones for presentation at the symposium. The topics covered include network and mobile access control, access control in applications, policy engineering, access control specification and access control enforcement. \u0000 \u0000In addition to the main research paper sessions, the symposium offers a panel discussion session entitled \"Security and privacy in the era of Internet of Things: research opportunities and challenges\", and a poster session. Above all, the conference proudly presents three exciting keynote talks by Virgil Gligor of Carnegie Mellon University, Bhavani Thuraisingham of University of Texas at Dallas, and Robert Deng of Singapore Management University, respectively.","PeriodicalId":423087,"journal":{"name":"Proceedings of the 23nd ACM on Symposium on Access Control Models and Technologies","volume":"95 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2016-06-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"133877717","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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