Sensitive information is present on our phones, disks, watches and computers. Its protection is essential. Plausible deniability of stored data allows individuals to deny that their device contains a piece of sensitive information. This constitutes a key tool in the fight against oppressive governments and censorship. Unfortunately, existing solutions, such as the now defunct TrueCrypt [2], can defend only against an adversary that can access a user's device at most once ("single-snapshot adversary"). Recent solutions have traded significant performance overheads for the ability to handle more powerful adversaries able to access the device at multiple points in time ("multi-snapshot adversary"). In this paper we show that this sacrifice is not necessary. We introduce and build DataLair, a practical plausible deniability mechanism. When compared with existing approaches, DataLair is two orders of magnitude faster (and as efficient as the underlying raw storage) for public data accesses, and 3-5 times faster for hidden data accesses. An important component in DataLair is a new, efficient write-only ORAM construction, which provides an improved access complexity when compared to the state-of-the-art.
{"title":"POSTER: DataLair: A Storage Block Device with Plausible Deniability","authors":"Anrin Chakraborti, Cheng Chen, R. Sion","doi":"10.1145/2976749.2989061","DOIUrl":"https://doi.org/10.1145/2976749.2989061","url":null,"abstract":"Sensitive information is present on our phones, disks, watches and computers. Its protection is essential. Plausible deniability of stored data allows individuals to deny that their device contains a piece of sensitive information. This constitutes a key tool in the fight against oppressive governments and censorship. Unfortunately, existing solutions, such as the now defunct TrueCrypt [2], can defend only against an adversary that can access a user's device at most once (\"single-snapshot adversary\"). Recent solutions have traded significant performance overheads for the ability to handle more powerful adversaries able to access the device at multiple points in time (\"multi-snapshot adversary\"). In this paper we show that this sacrifice is not necessary. We introduce and build DataLair, a practical plausible deniability mechanism. When compared with existing approaches, DataLair is two orders of magnitude faster (and as efficient as the underlying raw storage) for public data accesses, and 3-5 times faster for hidden data accesses. An important component in DataLair is a new, efficient write-only ORAM construction, which provides an improved access complexity when compared to the state-of-the-art.","PeriodicalId":432261,"journal":{"name":"Proceedings of the 2016 ACM SIGSAC Conference on Computer and Communications Security","volume":"16 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2016-10-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"116219329","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}
G. Barthe, Sonia Belaïd, François Dupressoir, Pierre-Alain Fouque, B. Grégoire, Pierre-Yves Strub, Rébecca Zucchini
Differential power analysis (DPA) is a side-channel attack in which an adversary retrieves cryptographic material by measuring and analyzing the power consumption of the device on which the cryptographic algorithm under attack executes. An effective countermeasure against DPA is to mask secrets by probabilistically encoding them over a set of shares, and to run masked algorithms that compute on these encodings. Masked algorithms are often expected to provide, at least, a certain level of probing security. Leveraging the deep connections between probabilistic information flow and probing security, we develop a precise, scalable, and fully automated methodology to verify the probing security of masked algorithms, and generate them from unprotected descriptions of the algorithm. Our methodology relies on several contributions of independent interest, including a stronger notion of probing security that supports compositional reasoning, and a type system for enforcing an expressive class of probing policies. Finally, we validate our methodology on examples that go significantly beyond the state-of-the-art.
{"title":"Strong Non-Interference and Type-Directed Higher-Order Masking","authors":"G. Barthe, Sonia Belaïd, François Dupressoir, Pierre-Alain Fouque, B. Grégoire, Pierre-Yves Strub, Rébecca Zucchini","doi":"10.1145/2976749.2978427","DOIUrl":"https://doi.org/10.1145/2976749.2978427","url":null,"abstract":"Differential power analysis (DPA) is a side-channel attack in which an adversary retrieves cryptographic material by measuring and analyzing the power consumption of the device on which the cryptographic algorithm under attack executes. An effective countermeasure against DPA is to mask secrets by probabilistically encoding them over a set of shares, and to run masked algorithms that compute on these encodings. Masked algorithms are often expected to provide, at least, a certain level of probing security. Leveraging the deep connections between probabilistic information flow and probing security, we develop a precise, scalable, and fully automated methodology to verify the probing security of masked algorithms, and generate them from unprotected descriptions of the algorithm. Our methodology relies on several contributions of independent interest, including a stronger notion of probing security that supports compositional reasoning, and a type system for enforcing an expressive class of probing policies. Finally, we validate our methodology on examples that go significantly beyond the state-of-the-art.","PeriodicalId":432261,"journal":{"name":"Proceedings of the 2016 ACM SIGSAC Conference on Computer and Communications Security","volume":"27 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2016-10-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"123089225","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 utilization of information hiding is on the rise among cybercriminals, e.g. to cloak the communication of malicious software as well as by ordinary users for privacy-enhancing purposes. A recent trend is to use network traffic in form of covert channels to convey secrets. In result, security expert training is incomplete if these aspects are not covered. This paper fills this gap by providing a method for teaching covert channel analysis of network protocols. We define a sample protocol called Covert Channel Educational Analysis Protocol (CCEAP) that can be used in didactic environments. Compared to previous works we lower the barrier for understanding network covert channels by eliminating the requirement for students to understand several network protocols in advance and by focusing on so-called hiding patterns.
{"title":"POSTER: An Educational Network Protocol for Covert Channel Analysis Using Patterns","authors":"S. Wendzel, W. Mazurczyk","doi":"10.1145/2976749.2989037","DOIUrl":"https://doi.org/10.1145/2976749.2989037","url":null,"abstract":"The utilization of information hiding is on the rise among cybercriminals, e.g. to cloak the communication of malicious software as well as by ordinary users for privacy-enhancing purposes. A recent trend is to use network traffic in form of covert channels to convey secrets. In result, security expert training is incomplete if these aspects are not covered. This paper fills this gap by providing a method for teaching covert channel analysis of network protocols. We define a sample protocol called Covert Channel Educational Analysis Protocol (CCEAP) that can be used in didactic environments. Compared to previous works we lower the barrier for understanding network covert channels by eliminating the requirement for students to understand several network protocols in advance and by focusing on so-called hiding patterns.","PeriodicalId":432261,"journal":{"name":"Proceedings of the 2016 ACM SIGSAC Conference on Computer and Communications Security","volume":"43 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2016-10-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"124475397","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}
My work that is being recognized by the 2015 ACM A. M. Turing Award is in cybersecurity, while my primary interest for the last thirty-five years is concerned with reducing the risk that nuclear deterrence will fail and destroy civilization. This Turing Lecture draws connections between those seemingly disparate areas as well as Alan Turing's elegant proof that the computable real numbers, while denumerable, are not effectively denumerable.
{"title":"Cybersecurity, Nuclear Security, Alan Turing, and Illogical Logic","authors":"M. Hellman","doi":"10.1145/2976749.2976757","DOIUrl":"https://doi.org/10.1145/2976749.2976757","url":null,"abstract":"My work that is being recognized by the 2015 ACM A. M. Turing Award is in cybersecurity, while my primary interest for the last thirty-five years is concerned with reducing the risk that nuclear deterrence will fail and destroy civilization. This Turing Lecture draws connections between those seemingly disparate areas as well as Alan Turing's elegant proof that the computable real numbers, while denumerable, are not effectively denumerable.","PeriodicalId":432261,"journal":{"name":"Proceedings of the 2016 ACM SIGSAC Conference on Computer and Communications Security","volume":"9 12 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2016-10-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"122953679","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}
Enrico Bacis, S. Vimercati, S. Foresti, S. Paraboschi, Marco Rosa, P. Samarati
We present an approach to enforce access revocation on resources stored at external cloud providers. The approach relies on a resource transformation that provides strong mutual inter-dependency in its encrypted representation. To revoke access on a resource, it is then sufficient to update a small portion of it, with the guarantee that the resource as a whole (and any portion of it) will become unintelligible to those from whom access is revoked. The extensive experimental evaluation on a variety of configurations confirmed the effectiveness and efficiency of our solution, which showed excellent performance and compatibility with several implementation strategies.
{"title":"Mix&Slice: Efficient Access Revocation in the Cloud","authors":"Enrico Bacis, S. Vimercati, S. Foresti, S. Paraboschi, Marco Rosa, P. Samarati","doi":"10.1145/2976749.2978377","DOIUrl":"https://doi.org/10.1145/2976749.2978377","url":null,"abstract":"We present an approach to enforce access revocation on resources stored at external cloud providers. The approach relies on a resource transformation that provides strong mutual inter-dependency in its encrypted representation. To revoke access on a resource, it is then sufficient to update a small portion of it, with the guarantee that the resource as a whole (and any portion of it) will become unintelligible to those from whom access is revoked. The extensive experimental evaluation on a variety of configurations confirmed the effectiveness and efficiency of our solution, which showed excellent performance and compatibility with several implementation strategies.","PeriodicalId":432261,"journal":{"name":"Proceedings of the 2016 ACM SIGSAC Conference on Computer and Communications Security","volume":"22 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2016-10-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"123503805","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}
Covert channels present serious security threat because they allow secret communication between two malicious processes even if the system inhibits direct communication. We describe, implement and quantify a new covert channel through shared hardware random number generation (RNG) module that is available on modern processors. We demonstrate that a reliable, high-capacity and low-error covert channel can be created through the RNG module that works across CPU cores and across virtual machines. We quantify the capacity of the RNG channel under different settings and show that transmission rates in the range of 7-200 kbit/s can be achieved depending on a particular system used for transmission, assumptions, and the load level. Finally, we describe challenges in mitigating the RNG channel, and propose several mitigation approaches both in software and hardware.
{"title":"Covert Channels through Random Number Generator: Mechanisms, Capacity Estimation and Mitigations","authors":"Dmitry Evtyushkin, D. Ponomarev","doi":"10.1145/2976749.2978374","DOIUrl":"https://doi.org/10.1145/2976749.2978374","url":null,"abstract":"Covert channels present serious security threat because they allow secret communication between two malicious processes even if the system inhibits direct communication. We describe, implement and quantify a new covert channel through shared hardware random number generation (RNG) module that is available on modern processors. We demonstrate that a reliable, high-capacity and low-error covert channel can be created through the RNG module that works across CPU cores and across virtual machines. We quantify the capacity of the RNG channel under different settings and show that transmission rates in the range of 7-200 kbit/s can be achieved depending on a particular system used for transmission, assumptions, and the load level. Finally, we describe challenges in mitigating the RNG channel, and propose several mitigation approaches both in software and hardware.","PeriodicalId":432261,"journal":{"name":"Proceedings of the 2016 ACM SIGSAC Conference on Computer and Communications Security","volume":"94 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2016-10-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"122075843","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}
Content Security Policy (CSP) is an emerging W3C standard introduced to mitigate the impact of content injection vulnerabilities on websites. We perform a systematic, large-scale analysis of four key aspects that impact on the effectiveness of CSP: browser support, website adoption, correct configuration and constant maintenance. While browser support is largely satisfactory, with the exception of few notable issues, our analysis unveils several shortcomings relative to the other three aspects. CSP appears to have a rather limited deployment as yet and, more crucially, existing policies exhibit a number of weaknesses and misconfiguration errors. Moreover, content security policies are not regularly updated to ban insecure practices and remove unintended security violations. We argue that many of these problems can be fixed by better exploiting the monitoring facilities of CSP, while other issues deserve additional research, being more rooted into the CSP design.
{"title":"Content Security Problems?: Evaluating the Effectiveness of Content Security Policy in the Wild","authors":"Stefano Calzavara, Alvise Rabitti, M. Bugliesi","doi":"10.1145/2976749.2978338","DOIUrl":"https://doi.org/10.1145/2976749.2978338","url":null,"abstract":"Content Security Policy (CSP) is an emerging W3C standard introduced to mitigate the impact of content injection vulnerabilities on websites. We perform a systematic, large-scale analysis of four key aspects that impact on the effectiveness of CSP: browser support, website adoption, correct configuration and constant maintenance. While browser support is largely satisfactory, with the exception of few notable issues, our analysis unveils several shortcomings relative to the other three aspects. CSP appears to have a rather limited deployment as yet and, more crucially, existing policies exhibit a number of weaknesses and misconfiguration errors. Moreover, content security policies are not regularly updated to ban insecure practices and remove unintended security violations. We argue that many of these problems can be fixed by better exploiting the monitoring facilities of CSP, while other issues deserve additional research, being more rooted into the CSP design.","PeriodicalId":432261,"journal":{"name":"Proceedings of the 2016 ACM SIGSAC Conference on Computer and Communications Security","volume":"1 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2016-10-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"129987142","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}
Random walks form a critical foundation in many social network based security systems and applications. Currently, the design of such social security mechanisms is limited to the classical paradigm of using fixed-length random walks for all nodes on a social graph. However, the fixed-length walk paradigm induces a poor trade-off between security and other desirable properties. In this paper, we propose SmartWalk, a security enhancing system which incorporates adaptive random walks in social network security applications. We utilize a set of supervised machine learning techniques to predict the necessary random walk length based on the structural characteristics of a social graph. Using experiments on multiple real world topologies, we show that the desired walk length starting from a specific node can be well predicted given the local features of the node, and limited knowledge for a small set of training nodes. We describe node-adaptive and path-adaptive random walk usage models, where the walk length adaptively changes based on the starting node and the intermediate nodes on the path, respectively. We experimentally demonstrate the applicability of adaptive random walks on a number of social network based security and privacy systems, including Sybil defenses, anonymous communication and link privacy preserving systems, and show up to two orders of magnitude improvement in performance.
{"title":"SmartWalk: Enhancing Social Network Security via Adaptive Random Walks","authors":"Yushan Liu, S. Ji, Prateek Mittal","doi":"10.1145/2976749.2978319","DOIUrl":"https://doi.org/10.1145/2976749.2978319","url":null,"abstract":"Random walks form a critical foundation in many social network based security systems and applications. Currently, the design of such social security mechanisms is limited to the classical paradigm of using fixed-length random walks for all nodes on a social graph. However, the fixed-length walk paradigm induces a poor trade-off between security and other desirable properties. In this paper, we propose SmartWalk, a security enhancing system which incorporates adaptive random walks in social network security applications. We utilize a set of supervised machine learning techniques to predict the necessary random walk length based on the structural characteristics of a social graph. Using experiments on multiple real world topologies, we show that the desired walk length starting from a specific node can be well predicted given the local features of the node, and limited knowledge for a small set of training nodes. We describe node-adaptive and path-adaptive random walk usage models, where the walk length adaptively changes based on the starting node and the intermediate nodes on the path, respectively. We experimentally demonstrate the applicability of adaptive random walks on a number of social network based security and privacy systems, including Sybil defenses, anonymous communication and link privacy preserving systems, and show up to two orders of magnitude improvement in performance.","PeriodicalId":432261,"journal":{"name":"Proceedings of the 2016 ACM SIGSAC Conference on Computer and Communications Security","volume":"2 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2016-10-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"129637300","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}
Public cloud vendors have been offering varies big data computing services. However, runtime integrity is one of the major concerns that hinders the adoption of those services. In this paper, we focus on MapReduce, a popular big data computing framework, propose the runtime integrity audition (RIA), a solution to verify the runtime integrity of MapReduce applications. Based on the idea of RIA, we developed a prototype system, called MR Auditor, and tested its applicability and the performance with multiple Hadoop applications. Our experimental results showed that MR Auditor is an efficient tool to detect runtime integrity violation and incurs a moderate performance overhead.
{"title":"POSTER: RIA: an Audition-based Method to Protect the Runtime Integrity of MapReduce Applications","authors":"Yongzhi Wang, Yulong Shen","doi":"10.1145/2976749.2989042","DOIUrl":"https://doi.org/10.1145/2976749.2989042","url":null,"abstract":"Public cloud vendors have been offering varies big data computing services. However, runtime integrity is one of the major concerns that hinders the adoption of those services. In this paper, we focus on MapReduce, a popular big data computing framework, propose the runtime integrity audition (RIA), a solution to verify the runtime integrity of MapReduce applications. Based on the idea of RIA, we developed a prototype system, called MR Auditor, and tested its applicability and the performance with multiple Hadoop applications. Our experimental results showed that MR Auditor is an efficient tool to detect runtime integrity violation and incurs a moderate performance overhead.","PeriodicalId":432261,"journal":{"name":"Proceedings of the 2016 ACM SIGSAC Conference on Computer and Communications Security","volume":"70 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2016-10-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"125420140","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}
Encrypting Internet communications has been the subject of renewed focus in recent years. In order to add end-to-end encryption to legacy applications without losing the convenience of full-text search, ShadowCrypt and Mimesis Aegis use a new cryptographic technique called "efficiently deployable efficiently searchable encryption" (EDESE) that allows a standard full-text search system to perform searches on encrypted data. Compared to other recent techniques for searching on encrypted data, EDESE schemes leak a great deal of statistical information about the encrypted messages and the keywords they contain. Until now, the practical impact of this leakage has been difficult to quantify. In this paper, we show that the adversary's task of matching plaintext keywords to the opaque cryptographic identifiers used in EDESE can be reduced to the well-known combinatorial optimization problem of weighted graph matching (WGM). Using real email and chat data, we show how off-the-shelf WGM solvers can be used to accurately and efficiently recover hundreds of the most common plaintext keywords from a set of EDESE-encrypted messages. We show how to recover the tags from Bloom filters so that the WGM solver can be used with the set of encrypted messages that utilizes a Bloom filter to encode its search tags. We also show that the attack can be mitigated by carefully configuring Bloom filter parameters.
{"title":"The Shadow Nemesis: Inference Attacks on Efficiently Deployable, Efficiently Searchable Encryption","authors":"D. Pouliot, C. V. Wright","doi":"10.1145/2976749.2978401","DOIUrl":"https://doi.org/10.1145/2976749.2978401","url":null,"abstract":"Encrypting Internet communications has been the subject of renewed focus in recent years. In order to add end-to-end encryption to legacy applications without losing the convenience of full-text search, ShadowCrypt and Mimesis Aegis use a new cryptographic technique called \"efficiently deployable efficiently searchable encryption\" (EDESE) that allows a standard full-text search system to perform searches on encrypted data. Compared to other recent techniques for searching on encrypted data, EDESE schemes leak a great deal of statistical information about the encrypted messages and the keywords they contain. Until now, the practical impact of this leakage has been difficult to quantify. In this paper, we show that the adversary's task of matching plaintext keywords to the opaque cryptographic identifiers used in EDESE can be reduced to the well-known combinatorial optimization problem of weighted graph matching (WGM). Using real email and chat data, we show how off-the-shelf WGM solvers can be used to accurately and efficiently recover hundreds of the most common plaintext keywords from a set of EDESE-encrypted messages. We show how to recover the tags from Bloom filters so that the WGM solver can be used with the set of encrypted messages that utilizes a Bloom filter to encode its search tags. We also show that the attack can be mitigated by carefully configuring Bloom filter parameters.","PeriodicalId":432261,"journal":{"name":"Proceedings of the 2016 ACM SIGSAC Conference on Computer and Communications Security","volume":"48 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2016-10-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"132600334","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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