J. Zinzindohoué, Evmorfia-Iro Bartzia, K. Bhargavan
In response to increasing demand for elliptic curve cryptography, and specifically for curves that are free from the suspicion of influence by the NSA, new elliptic curves such as Curve25519 and Curve448 are currently being standardized, implemented, and deployed in major protocols such as Transport Layer Security. As with all new cryptographic code, the correctness of these curve implementations is of concern, because any bug or backdoor in this code can potentially compromise the security of important Internet protocols. We present a principled approach towards the verification of elliptic curve implementations by writing them in the dependently-typed programming language F* and proving them functionally correct against a readable mathematical specification derived from a previous Coq development. A key technical innovation in our work is the use of templates to write and verify arbitrary precision arithmetic once and for all for a variety of Bignum representations used in different curves. We also show how to use abstract types to enforce a coding discipline that mitigates side-channels at the source level. We present a verified F* library that implements the popular curves Curve25519, Curve448, and NIST-P256, and we show how developers can add new curves to this library with minimal programming and verification effort.
{"title":"A Verified Extensible Library of Elliptic Curves","authors":"J. Zinzindohoué, Evmorfia-Iro Bartzia, K. Bhargavan","doi":"10.1109/CSF.2016.28","DOIUrl":"https://doi.org/10.1109/CSF.2016.28","url":null,"abstract":"In response to increasing demand for elliptic curve cryptography, and specifically for curves that are free from the suspicion of influence by the NSA, new elliptic curves such as Curve25519 and Curve448 are currently being standardized, implemented, and deployed in major protocols such as Transport Layer Security. As with all new cryptographic code, the correctness of these curve implementations is of concern, because any bug or backdoor in this code can potentially compromise the security of important Internet protocols. We present a principled approach towards the verification of elliptic curve implementations by writing them in the dependently-typed programming language F* and proving them functionally correct against a readable mathematical specification derived from a previous Coq development. A key technical innovation in our work is the use of templates to write and verify arbitrary precision arithmetic once and for all for a variety of Bignum representations used in different curves. We also show how to use abstract types to enforce a coding discipline that mitigates side-channels at the source level. We present a verified F* library that implements the popular curves Curve25519, Curve448, and NIST-P256, and we show how developers can add new curves to this library with minimal programming and verification effort.","PeriodicalId":6500,"journal":{"name":"2016 IEEE 29th Computer Security Foundations Symposium (CSF)","volume":"6 1","pages":"296-309"},"PeriodicalIF":0.0,"publicationDate":"2016-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"90819894","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}
In cryptology, verifiable computing aims at verifying the remote execution of a program on an untrusted machine, based on its I/O and constant-sized evidence collected during its execution. Recent cryptographic schemes and compilers enable practical verifiable computations for some programs written in C, but their soundness with regards to C semantics remains informal and poorly understood. We present the first certified, semantics-preserving compiler for verifiable computing. Based on CompCert and developed in Coq, our compiler targets an architecture whose instructions consist solely of quadratic equations over a large finite field, amenable to succinct verification using the Pinocchio cryptographic scheme. We explain how to encode the integer operations of a C program first to quadratic equations, then to a single cryptographically-checkable polynomial test. We formally prove that, when compilation succeeds, there is a correct execution of the source program for any I/O that pass this test. We link our compiler to the Pinocchio cryptographic runtime, and report experimental results as we compile, run, and verify the execution of sample C programs.
{"title":"A Certified Compiler for Verifiable Computing","authors":"C. Fournet, C. Keller, Vincent Laporte","doi":"10.1109/CSF.2016.26","DOIUrl":"https://doi.org/10.1109/CSF.2016.26","url":null,"abstract":"In cryptology, verifiable computing aims at verifying the remote execution of a program on an untrusted machine, based on its I/O and constant-sized evidence collected during its execution. Recent cryptographic schemes and compilers enable practical verifiable computations for some programs written in C, but their soundness with regards to C semantics remains informal and poorly understood. We present the first certified, semantics-preserving compiler for verifiable computing. Based on CompCert and developed in Coq, our compiler targets an architecture whose instructions consist solely of quadratic equations over a large finite field, amenable to succinct verification using the Pinocchio cryptographic scheme. We explain how to encode the integer operations of a C program first to quadratic equations, then to a single cryptographically-checkable polynomial test. We formally prove that, when compilation succeeds, there is a correct execution of the source program for any I/O that pass this test. We link our compiler to the Pinocchio cryptographic runtime, and report experimental results as we compile, run, and verify the execution of sample C programs.","PeriodicalId":6500,"journal":{"name":"2016 IEEE 29th Computer Security Foundations Symposium (CSF)","volume":"7 1","pages":"268-280"},"PeriodicalIF":0.0,"publicationDate":"2016-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"77710008","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}
This paper introduces a novel runtime verification technique for a rich sub-class of Clarkson and Schneider's hyperproperties. The primary application of such properties is in expressing security policies (e.g., information flow) that cannot be expressed in trace-based specification languages (e.g., LTL). First, to incorporate syntactic means, we draw connections between safety and co-safety hyperproperties and the temporal logic HYPERLTL, which allows explicit quantification over multiple executions. We also define the notion of monitorability in HYPERLTL and identify classes of monitorable HYPERLTL formulas. Then, we introduce an algorithm for monitoring k-safety and co-k-safety hyperproperties expressed in HYPERLTL. Our technique is based on runtime formula progression as well as on-the-fly monitor synthesis across multiple executions. We analyze different performance aspects of our technique by conducting thorough experiments on monitoring security policies for information flow and observational determinism on a real-world location-based service dataset as well as synthetic trace sets.
{"title":"Runtime Verification of k-Safety Hyperproperties in HyperLTL","authors":"Shreya Agrawal, Borzoo Bonakdarpour","doi":"10.1109/CSF.2016.24","DOIUrl":"https://doi.org/10.1109/CSF.2016.24","url":null,"abstract":"This paper introduces a novel runtime verification technique for a rich sub-class of Clarkson and Schneider's hyperproperties. The primary application of such properties is in expressing security policies (e.g., information flow) that cannot be expressed in trace-based specification languages (e.g., LTL). First, to incorporate syntactic means, we draw connections between safety and co-safety hyperproperties and the temporal logic HYPERLTL, which allows explicit quantification over multiple executions. We also define the notion of monitorability in HYPERLTL and identify classes of monitorable HYPERLTL formulas. Then, we introduce an algorithm for monitoring k-safety and co-k-safety hyperproperties expressed in HYPERLTL. Our technique is based on runtime formula progression as well as on-the-fly monitor synthesis across multiple executions. We analyze different performance aspects of our technique by conducting thorough experiments on monitoring security policies for information flow and observational determinism on a real-world location-based service dataset as well as synthetic trace sets.","PeriodicalId":6500,"journal":{"name":"2016 IEEE 29th Computer Security Foundations Symposium (CSF)","volume":"24 1","pages":"239-252"},"PeriodicalIF":0.0,"publicationDate":"2016-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"87553188","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}
M. Cramer, Pieter Van Hertum, Ruben Lapauw, Ingmar Dasseville, M. Denecker
In ownership-based access control frameworks with the possibility of delegating permissions and administrative rights, chains of delegated accesses will form. There are different ways to treat these delegation chains when revoking rights, which give rise to different revocation schemes. One possibility studied in the literature is to revoke rights by issuing negative authorizations, meant to ensure that the revocation is resilient to a later reissuing of the rights, and to resolve conflicts between principals by giving precedence to predecessors, i.e. principals that come earlier in the delegation chain. However, the effects of negative authorizations have been defined differently by different authors. Having identified three definitions of this effect from the literature, the first contribution of this paper is to point out that two of these three definitions pose a security threat. However, avoiding this security threat comes at a price: We prove that with the safe definition of the effect of negative authorizations, deciding whether a principal does have access to a resource is an NP-complete decision problem. We discuss two limitations that can be imposed on an access-control system in order to reduce the complexity of the problem back to a polynomial complexity: Limiting the length of delegation chains to an integer m reduces the runtime complexity of determining access to O(nm), and requiring that principals form a hierarchy that graph-theoretically forms a rooted tree makes this decision problem solvable in quadratic runtime. Finally we discuss an approach that can mitigate the complexity problem in practice without fully getting rid of NP-completeness.
{"title":"Resilient Delegation Revocation with Precedence for Predecessors Is NP-Complete","authors":"M. Cramer, Pieter Van Hertum, Ruben Lapauw, Ingmar Dasseville, M. Denecker","doi":"10.1109/CSF.2016.37","DOIUrl":"https://doi.org/10.1109/CSF.2016.37","url":null,"abstract":"In ownership-based access control frameworks with the possibility of delegating permissions and administrative rights, chains of delegated accesses will form. There are different ways to treat these delegation chains when revoking rights, which give rise to different revocation schemes. One possibility studied in the literature is to revoke rights by issuing negative authorizations, meant to ensure that the revocation is resilient to a later reissuing of the rights, and to resolve conflicts between principals by giving precedence to predecessors, i.e. principals that come earlier in the delegation chain. However, the effects of negative authorizations have been defined differently by different authors. Having identified three definitions of this effect from the literature, the first contribution of this paper is to point out that two of these three definitions pose a security threat. However, avoiding this security threat comes at a price: We prove that with the safe definition of the effect of negative authorizations, deciding whether a principal does have access to a resource is an NP-complete decision problem. We discuss two limitations that can be imposed on an access-control system in order to reduce the complexity of the problem back to a polynomial complexity: Limiting the length of delegation chains to an integer m reduces the runtime complexity of determining access to O(nm), and requiring that principals form a hierarchy that graph-theoretically forms a rooted tree makes this decision problem solvable in quadratic runtime. Finally we discuss an approach that can mitigate the complexity problem in practice without fully getting rid of NP-completeness.","PeriodicalId":6500,"journal":{"name":"2016 IEEE 29th Computer Security Foundations Symposium (CSF)","volume":"34 1","pages":"432-442"},"PeriodicalIF":0.0,"publicationDate":"2016-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"87956006","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}
We present a system model, an enforcement mechanism, and a policy language for the proactive enforcement of timed provisions and obligations. Our approach improves upon existing formalisms in two ways: (1) we exploit the target system's existing functionality to avert policy violations proactively, rather than compensate for them reactively, and, (2) instead of requiring the manual specification of remedial actions in the policy, we automatically deduce required actions directly from the policy. As a policy language, we employ timed dynamic condition response (DCR) processes. DCR primitives declaratively express timed provisions and obligations as causal relationships between events, and DCR states explicitly represent pending obligations. As key technical results, we show that enforceability of DCR policies is decidable, we give a sufficient polynomial time verifiable condition for a policy to be enforceable, and we give an algorithm for determining from a DCR state a sequence of actions that discharge impending obligations.
{"title":"In the Nick of Time: Proactive Prevention of Obligation Violations","authors":"D. Basin, S. Debois, Thomas T. Hildebrandt","doi":"10.1109/CSF.2016.16","DOIUrl":"https://doi.org/10.1109/CSF.2016.16","url":null,"abstract":"We present a system model, an enforcement mechanism, and a policy language for the proactive enforcement of timed provisions and obligations. Our approach improves upon existing formalisms in two ways: (1) we exploit the target system's existing functionality to avert policy violations proactively, rather than compensate for them reactively, and, (2) instead of requiring the manual specification of remedial actions in the policy, we automatically deduce required actions directly from the policy. As a policy language, we employ timed dynamic condition response (DCR) processes. DCR primitives declaratively express timed provisions and obligations as causal relationships between events, and DCR states explicitly represent pending obligations. As key technical results, we show that enforceability of DCR policies is decidable, we give a sufficient polynomial time verifiable condition for a policy to be enforceable, and we give an algorithm for determining from a DCR state a sequence of actions that discharge impending obligations.","PeriodicalId":6500,"journal":{"name":"2016 IEEE 29th Computer Security Foundations Symposium (CSF)","volume":"57 1","pages":"120-134"},"PeriodicalIF":0.0,"publicationDate":"2016-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"80227128","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}
Confidentiality of training data induced by releasing machine-learning models, and has recently received increasing attention. Motivated by existing MI attacks and other previous attacks that turn out to be MI "in disguise," this paper initiates a formal study of MI attacks by presenting a game-based methodology. Our methodology uncovers a number of subtle issues, and devising a rigorous game-based definition, analogous to those in cryptography, is an interesting avenue for future work. We describe methodologies for two types of attacks. The first is for black-box attacks, which consider an adversary who infers sensitive values with only oracle access to a model. The second methodology targets the white-box scenario where an adversary has some additional knowledge about the structure of a model. For the restricted class of Boolean models and black-box attacks, we characterize model invertibility using the concept of influence from Boolean analysis in the noiseless case, and connect model invertibility with stable influence in the noisy case. Interestingly, we also discovered an intriguing phenomenon, which we call "invertibility interference," where a highly invertible model quickly becomes highly non-invertible by adding little noise. For the white-box case, we consider a common phenomenon in machine-learning models where the model is a sequential composition of several sub-models. We show, quantitatively, that even very restricted communication between layers could leak a significant amount of information. Perhaps more importantly, our study also unveils unexpected computational power of these restricted communication channels, which, to the best of our knowledge, were not previously known.
{"title":"A Methodology for Formalizing Model-Inversion Attacks","authors":"Xi Wu, Matt Fredrikson, S. Jha, J. Naughton","doi":"10.1109/CSF.2016.32","DOIUrl":"https://doi.org/10.1109/CSF.2016.32","url":null,"abstract":"Confidentiality of training data induced by releasing machine-learning models, and has recently received increasing attention. Motivated by existing MI attacks and other previous attacks that turn out to be MI \"in disguise,\" this paper initiates a formal study of MI attacks by presenting a game-based methodology. Our methodology uncovers a number of subtle issues, and devising a rigorous game-based definition, analogous to those in cryptography, is an interesting avenue for future work. We describe methodologies for two types of attacks. The first is for black-box attacks, which consider an adversary who infers sensitive values with only oracle access to a model. The second methodology targets the white-box scenario where an adversary has some additional knowledge about the structure of a model. For the restricted class of Boolean models and black-box attacks, we characterize model invertibility using the concept of influence from Boolean analysis in the noiseless case, and connect model invertibility with stable influence in the noisy case. Interestingly, we also discovered an intriguing phenomenon, which we call \"invertibility interference,\" where a highly invertible model quickly becomes highly non-invertible by adding little noise. For the white-box case, we consider a common phenomenon in machine-learning models where the model is a sequential composition of several sub-models. We show, quantitatively, that even very restricted communication between layers could leak a significant amount of information. Perhaps more importantly, our study also unveils unexpected computational power of these restricted communication channels, which, to the best of our knowledge, were not previously known.","PeriodicalId":6500,"journal":{"name":"2016 IEEE 29th Computer Security Foundations Symposium (CSF)","volume":"30 6","pages":"355-370"},"PeriodicalIF":0.0,"publicationDate":"2016-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"91455157","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}
A fundamental challenge in controlling the leakage of sensitive information by computer systems is the possibility of correlations between different secrets, with the result that leaking information about one secret may also leak information about a different secret. We explore such leakage, here called Dalenius leakage, within the context of the g-leakage family of leakage measures. We prove a fundamental equivalence between Dalenius min-entropy leakage under arbitrary correlations and g-leakage under arbitrary gain functions, and show how this equivalence increases the significance of the composition refinement relation. We also consider Dalenius leakage in the case when the marginal distributions induced by the correlation are known, giving techniques to compute stronger upper bounds in this case.
{"title":"Correlated Secrets in Quantitative Information Flow","authors":"N. E. Bordenabe, Geoffrey Smith","doi":"10.1109/CSF.2016.14","DOIUrl":"https://doi.org/10.1109/CSF.2016.14","url":null,"abstract":"A fundamental challenge in controlling the leakage of sensitive information by computer systems is the possibility of correlations between different secrets, with the result that leaking information about one secret may also leak information about a different secret. We explore such leakage, here called Dalenius leakage, within the context of the g-leakage family of leakage measures. We prove a fundamental equivalence between Dalenius min-entropy leakage under arbitrary correlations and g-leakage under arbitrary gain functions, and show how this equivalence increases the significance of the composition refinement relation. We also consider Dalenius leakage in the case when the marginal distributions induced by the correlation are known, giving techniques to compute stronger upper bounds in this case.","PeriodicalId":6500,"journal":{"name":"2016 IEEE 29th Computer Security Foundations Symposium (CSF)","volume":"1 1","pages":"93-104"},"PeriodicalIF":0.0,"publicationDate":"2016-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"91322352","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}
Fine grained information flow monitoring can in principle address a wide range of security and privacy goals, for example in web applications. But it is very difficult to achieve sound monitoring with acceptable runtime cost and sufficient precision to avoid impractical restrictions on programs and policies. We present a systematic technique for design of monitors that are correct by construction. It encompasses policies with downgrading. The technique is based on abstract interpretation which is a standard basis for static analysis of programs. This should enable integration of a wide range of analysis techniques, enabling more sophisticated engineering of monitors to address the challenges of precision and scaling to widely used programming languages.
{"title":"Calculational Design of Information Flow Monitors","authors":"Mounir Assaf, D. Naumann","doi":"10.1109/CSF.2016.22","DOIUrl":"https://doi.org/10.1109/CSF.2016.22","url":null,"abstract":"Fine grained information flow monitoring can in principle address a wide range of security and privacy goals, for example in web applications. But it is very difficult to achieve sound monitoring with acceptable runtime cost and sufficient precision to avoid impractical restrictions on programs and policies. We present a systematic technique for design of monitors that are correct by construction. It encompasses policies with downgrading. The technique is based on abstract interpretation which is a standard basis for static analysis of programs. This should enable integration of a wide range of analysis techniques, enabling more sophisticated engineering of monitors to address the challenges of precision and scaling to widely used programming languages.","PeriodicalId":6500,"journal":{"name":"2016 IEEE 29th Computer Security Foundations Symposium (CSF)","volume":"53 1","pages":"210-224"},"PeriodicalIF":0.0,"publicationDate":"2016-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"88537304","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}
Observational equivalence allows us to study important security properties such as anonymity. Unfortunately, the difficulty of proving observational equivalence hinders analysis. Blanchet, Abadi & Fournet simplify its proof by introducing a sufficient condition for observational equivalence, called diff-equivalence, which is a reachability condition that can be proved automatically by ProVerif. However, diff-equivalence is a very strong condition, which often does not hold even if observational equivalence does. In particular, when proving equivalence between processes that contain several parallel components, e.g., P | Q and P' | Q', diff-equivalence requires that P is equivalent to P' and Q is equivalent to Q'. To relax this constraint, Delaune, Ryan & Smyth introduced the idea of swapping data between parallel processes P' and Q' at synchronisation points, without proving its soundness. We extend their work by formalising the semantics of synchronisation, formalising the definition of swapping, and proving its soundness. We also relax some restrictions they had on the processes to which swapping can be applied. Moreover, we have implemented our results in ProVerif. Hence, we extend the class of equivalences that can be proved automatically. We showcase our results by analysing privacy in election schemes by Fujioka, Okamoto & Ohta and Lee et al., and in the vehicular ad-hoc network by Freudiger et al.
{"title":"Automated Reasoning for Equivalences in the Applied Pi Calculus with Barriers","authors":"B. Blanchet, B. Smyth","doi":"10.1109/CSF.2016.29","DOIUrl":"https://doi.org/10.1109/CSF.2016.29","url":null,"abstract":"Observational equivalence allows us to study important security properties such as anonymity. Unfortunately, the difficulty of proving observational equivalence hinders analysis. Blanchet, Abadi & Fournet simplify its proof by introducing a sufficient condition for observational equivalence, called diff-equivalence, which is a reachability condition that can be proved automatically by ProVerif. However, diff-equivalence is a very strong condition, which often does not hold even if observational equivalence does. In particular, when proving equivalence between processes that contain several parallel components, e.g., P | Q and P' | Q', diff-equivalence requires that P is equivalent to P' and Q is equivalent to Q'. To relax this constraint, Delaune, Ryan & Smyth introduced the idea of swapping data between parallel processes P' and Q' at synchronisation points, without proving its soundness. We extend their work by formalising the semantics of synchronisation, formalising the definition of swapping, and proving its soundness. We also relax some restrictions they had on the processes to which swapping can be applied. Moreover, we have implemented our results in ProVerif. Hence, we extend the class of equivalences that can be proved automatically. We showcase our results by analysing privacy in election schemes by Fujioka, Okamoto & Ohta and Lee et al., and in the vehicular ad-hoc network by Freudiger et al.","PeriodicalId":6500,"journal":{"name":"2016 IEEE 29th Computer Security Foundations Symposium (CSF)","volume":"277 1","pages":"310-324"},"PeriodicalIF":0.0,"publicationDate":"2016-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"73285224","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}
Stefano Calzavara, Alvise Rabitti, Enrico Steffinlongo, M. Bugliesi
Authorization in workflow systems is usually built on top of role-based access control (RBAC), security policies on workflows are then expressed as constraints on the users performing a set of tasks and the roles assigned to them. Unfortunately, when role administration is distributed and potentially untrusted users contribute to the role assignment process, like in the case of Administrative RBAC (ARBAC), collusions may take place to circumvent the intended workflow security policies. In a collusion attack, a set of users of a workflow system collaborates by changing the user-to-role assignment, so as to sidestep the security policies and run up to completion a workflow they could not complete otherwise. In this paper, we study the problem of collusion attacks in a formal model of workflows based on stable event structures and we define a precise notion of security against collusion. We then propose a static analysis technique based on a reduction to a role reachability problem for ARBAC, which can be used to prove or disprove security for a large class of workflow systems. We also discuss how to aggressively optimise the obtained role reachability problem to ensure its tractability. Finally, we implement our analysis in a tool, WARBAC, and we experimentally show its effectiveness on a set of publicly available examples, including a realistic case study.
{"title":"Static Detection of Collusion Attacks in ARBAC-Based Workflow Systems","authors":"Stefano Calzavara, Alvise Rabitti, Enrico Steffinlongo, M. Bugliesi","doi":"10.1109/CSF.2016.39","DOIUrl":"https://doi.org/10.1109/CSF.2016.39","url":null,"abstract":"Authorization in workflow systems is usually built on top of role-based access control (RBAC), security policies on workflows are then expressed as constraints on the users performing a set of tasks and the roles assigned to them. Unfortunately, when role administration is distributed and potentially untrusted users contribute to the role assignment process, like in the case of Administrative RBAC (ARBAC), collusions may take place to circumvent the intended workflow security policies. In a collusion attack, a set of users of a workflow system collaborates by changing the user-to-role assignment, so as to sidestep the security policies and run up to completion a workflow they could not complete otherwise. In this paper, we study the problem of collusion attacks in a formal model of workflows based on stable event structures and we define a precise notion of security against collusion. We then propose a static analysis technique based on a reduction to a role reachability problem for ARBAC, which can be used to prove or disprove security for a large class of workflow systems. We also discuss how to aggressively optimise the obtained role reachability problem to ensure its tractability. Finally, we implement our analysis in a tool, WARBAC, and we experimentally show its effectiveness on a set of publicly available examples, including a realistic case study.","PeriodicalId":6500,"journal":{"name":"2016 IEEE 29th Computer Security Foundations Symposium (CSF)","volume":"1 1","pages":"458-470"},"PeriodicalIF":0.0,"publicationDate":"2016-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"87036644","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}
京公网安备 11010802042870号
京ICP备2023020795号-1
扫码关注我们
求助内容：
应助结果提醒方式：