25th IEEE International Conference on Distributed Computing Systems Workshops, 2005
Popularity of peer-to-peer (P2P) networks exposed a number of security vulnerabilities including ... more Popularity of peer-to-peer (P2P) networks exposed a number of security vulnerabilities including the problem of finding reliable communication partners. In this paper, we present an integrated trust framework for P2P networks that quantifies the trustworthiness of a peer using reputation-based trust mechanism and anomaly detection technique. We describe anomaly detection procedure that analyzes peer activity on the network and flags potentially malicious behavior by detecting deviation from peer profile. We study the performance of our trust framework using simulation and compare it with the existing reputation-based system which does not employ an anomaly detection mechanism.
We present a methodology and corresponding implementation that, given a program and a correctness... more We present a methodology and corresponding implementation that, given a program and a correctness assertion violated by the program, identifies a set of focus statements that captures in the most succinct manner possible the cause of the violation. Our method, which is based on program dependency analysis, also automatically identifies feasible counter-examples and presents the user with sets of constraints over program variables necessary for their feasibility. We illustrate the practical utility of our approach via its successful application to the Resolution Advisory module of the Traffic Collision Avoidance system (TCAS).
Model checking involves exploring state-space of system model and automatically proving or dispro... more Model checking involves exploring state-space of system model and automatically proving or disproving the correct functionality of the system. Verification of all properties may not require exploration of the state-space in its entirety. However, traditional model checkers are not equipped with enough knowledge of the system apriori to make smart decisions so as to explore only those portions of state-space that contribute to the result. In this paper, we present a technique to provide such guidance to the model checker so that it can perform state-space exploration more intelligently. We incorporated our technique in XMC model checker, a tool for verifying process expressions in CCS against properties expressed by modal mu-calculus formulas. We demonstrate the applicability of our guidance mechanism by verifying several example protocols from XMC test-suite.
Protocol conversion problem involves identifying whether two or more protocols can be composed wi... more Protocol conversion problem involves identifying whether two or more protocols can be composed with or without an intermediary, referred to as a converter, to obtain a pre-specified desired behavior. We investigate this problem in formal setting and propose, for the first time, a temporal logic based automatic solution to the convertibility verification and synthesis. At its core, our technique is based on local model checking technique and determines the existence of the converter and if a converter exists, it is automatically synthesized. A number of key features of our technique distinguishes it from all existing formal and/or informal techniques. Firstly, we handle both data and control mismatches (for the first time), using a single unifying model checking based solution. Secondly, the proposed approach uses temporal logic for the specification of correct behaviors (unlike earlier automaton based specifications) which is both elegant and natural to express event ordering and data-matching requirements. Finally, we have have experimented extensively with the examples available in the existing literature to evaluate the applicability of our technique in wide range of applications.
Web services are fast emerging as the technology of choice to build distributed information syste... more Web services are fast emerging as the technology of choice to build distributed information systems in multiple domains including e-Business and e-Science. An important challenge is to develop methodologies and tools that enable (semi-) automatic composition of services by taking into account the functional, non-functional and behavioral requirements of the service developer. This paper presents the fundamental concepts and issues related to service composition and provides a representative sample of existing work proposed by the AI planning and formal methods communities to address some of the challenges in service composition. It also provides a brief introduction to an iterative and incremental technique for modeling composite Web services proposed by the authors.
Parameterized systems verication is a long-standing problem, where the challenge is to verify tha... more Parameterized systems verication is a long-standing problem, where the challenge is to verify that a property holds for all (innite) instances of the parameterized system. Existing techniques aim to reduce this problem to checking the properties on smaller systems with a bound on the parameter referred to as the cut-o such that if the property holds for system instances of size cut-o that implies that it holds for larger system instances. In most existing techniques, human guidance is required to deduce the invariants for the system's behavior, which are then used to compute cut-o. In contrast, we present an fully automatic sound method (but necessarily incomplete) for generating the cut-o that works for synchronous parameterized systems with heterogeneous processes communicating via single-cast and/or broadcast. Our technique is independent of the system topology and the property to be veried. Given the specication and the topology of the system, our technique generates the system-specic cut-o. We have realized our technique in a tool, Golok, which shows that it can be automated. We present the results of running Golok on 15 parameterized systems where we obtain smaller cut-os than those presented in the existing literature for 14 cases.
We study the problem of statistical model checking of probabilistic systems for PCTL unbounded un... more We study the problem of statistical model checking of probabilistic systems for PCTL unbounded until property P1p(ϕ1 U ϕ2) (where 1 ∈ {<, ≤, >, ≥}) using the computation of P ≤0 (ϕ 1 U ϕ 2 ). The approach is first proposed by Sen et al.
Let X = {X i } be a set of variables, each with a domain D i . An outcome α ∈ O is a complete ass... more Let X = {X i } be a set of variables, each with a domain D i . An outcome α ∈ O is a complete assignment to all the variables, denoted by the tuple α := α(X 1 ), α(X 2 ), . . . , α(X m ) such that α(X i ) ∈ D i for each X i ∈ X . The set of all possible outcomes is given by O = Xi∈X D i . We consider a preference language L for specifying: (a) unconditional intra-variable preferences ≻ i that are strict partial orders (i.e., irreflexive and transitive relations) over D i ; and (b) unconditional relative importance preferences that are strict partial orders over X .
Web services are software entities which provide a set of functionalities that can be accessed ov... more Web services are software entities which provide a set of functionalities that can be accessed over the Web. In general, the valuations of variables appearing in various functions provided by the service are not known before execution. Consequently, to analyze the behavior of a service, all possible valuations need to be considered, making the whole system infinite-state. Against this background, we propose a framework for modeling and composing Web services where desired (goal) and pre-existing (component) services exhibit infinite-state behavior. Our approach finitely represents such services using Symbolic Transition Systems (STSs) which are transition systems augmented with guards over infinitedomain variables. We develop a sound and complete logical approach for identifying the existence of composition of available component-STSs, such that the resulting composition is "simulated" by the goal-STS. In the event that the goal service cannot be realized from the existing components, our technique can also identify the cause for the failure and guide the user to achieve appropriate refinement of the goal specification, thereby paving the way for incremental development of composite services.
Recent advances in the field of intrusion detection brought new requirements to intrusion prevent... more Recent advances in the field of intrusion detection brought new requirements to intrusion prevention and response. Tra-ditionally, the response to the detected attack was selected and deployed manually, in the recent years the focus has shifted towards developing automated and semi-automated methodologies for responding to intrusions. In this context, the cost-sensitive intrusion response models have gained the most interest mainly due to their emphasis on the balance between potential damage incurred by the intrusion and cost of the response. However, one of the challenges in applying this approach is defining consistent and adaptable measure-ment of these cost factors on the basis of requirements and policy of the system being protected against intrusions. In this paper we present a structured methodology for eval-uating cost of responses based on three factors: the response operational cost associated with the daily maintenance of the response, the response goodness that measures...
Spread of infections (diseases, ideas, etc.) in a network can be modeled as the evolution of stat... more Spread of infections (diseases, ideas, etc.) in a network can be modeled as the evolution of states of nodes in a graph as a function of the states of their neighbors. Given an initial configuration of a network in which a subset of the nodes have been infected, and an infec- tion propagation function that specifies how the states of the nodes evolve over time, we show how to use model checking to identify, verify, and evaluate the effective- ness of intervention policies for containing the propaga- tion of infection over such networks.
We study a dominance relation for comparing outcomes based on unconditional qualitative preferenc... more We study a dominance relation for comparing outcomes based on unconditional qualitative preferences and compare it with its unconditional counterparts for TCP-nets and their variants. Dominance testing based on this relation can be carried out in polynomial time by evaluating the satisfiability of a logic formula.
Dominance testing, the problem of determining whether an outcome is preferred over another, is of... more Dominance testing, the problem of determining whether an outcome is preferred over another, is of fundamental importance in many applications. Hence, there is a need for algorithms and tools for dominance testing. CP-nets and TCP-nets are some of the widely studied languages for representing and reasoning with preferences. We reduce dominance testing in TCP-nets to reachability analysis in a graph of outcomes. We provide an encoding of TCP-nets in the form of a Kripke structure for CTL. We show how to compute dominance using NuSMV, a model checker for CTL. We present results of experiments that demonstrate the feasibility of our approach to dominance testing.
2012 Design, Automation & Test in Europe Conference & Exhibition (DATE), 2012
Systems-on-chip (SoCs) contain multiple interconnected and interacting components. In this paper,... more Systems-on-chip (SoCs) contain multiple interconnected and interacting components. In this paper, we present a compositional approach for the integration of multiple components with a wide range of protocol mismatches into a single SoC. We show how SoC construction can be done in single-step when all components are integrated at once or it can also be performed incrementally by adding components to an already integrated design. Using a number of AMBA IPs, we show that the proposed framework is able to perform protocol conversion in many cases where existing approaches fail.
2009 Design, Automation & Test in Europe Conference & Exhibition, 2009
The automated design of SoCs from pre-selected IPs that may require different clocks is challengi... more The automated design of SoCs from pre-selected IPs that may require different clocks is challenging because of the following issues. Firstly, protocol mismatches between IPs need to be resolved automatically before IPs are integrated. Secondly, the presence of multiple clocks makes the protocol conversion even more difficult. Thirdly, it is desirable that the resulting integration is correct-by-construction, i.e., the resulting SoC satisfies given system-level specifications. All of these issues have been studied extensively, although not in a unifying manner. In this paper we propose a framework based on protocol conversion that addresses all these issues. We have extensively studied many SoC design problems and show that the proposed methodology is capable of handling them better than other known approaches. A significant contribution of the proposed approach is that it nicely generalizes many existing techniques for formal SoC design and integrates them into a single approach.
25th IEEE International Conference on Distributed Computing Systems Workshops, 2005
Popularity of peer-to-peer (P2P) networks exposed a number of security vulnerabilities including ... more Popularity of peer-to-peer (P2P) networks exposed a number of security vulnerabilities including the problem of finding reliable communication partners. In this paper, we present an integrated trust framework for P2P networks that quantifies the trustworthiness of a peer using reputation-based trust mechanism and anomaly detection technique. We describe anomaly detection procedure that analyzes peer activity on the network and flags potentially malicious behavior by detecting deviation from peer profile. We study the performance of our trust framework using simulation and compare it with the existing reputation-based system which does not employ an anomaly detection mechanism.
We present a methodology and corresponding implementation that, given a program and a correctness... more We present a methodology and corresponding implementation that, given a program and a correctness assertion violated by the program, identifies a set of focus statements that captures in the most succinct manner possible the cause of the violation. Our method, which is based on program dependency analysis, also automatically identifies feasible counter-examples and presents the user with sets of constraints over program variables necessary for their feasibility. We illustrate the practical utility of our approach via its successful application to the Resolution Advisory module of the Traffic Collision Avoidance system (TCAS).
Model checking involves exploring state-space of system model and automatically proving or dispro... more Model checking involves exploring state-space of system model and automatically proving or disproving the correct functionality of the system. Verification of all properties may not require exploration of the state-space in its entirety. However, traditional model checkers are not equipped with enough knowledge of the system apriori to make smart decisions so as to explore only those portions of state-space that contribute to the result. In this paper, we present a technique to provide such guidance to the model checker so that it can perform state-space exploration more intelligently. We incorporated our technique in XMC model checker, a tool for verifying process expressions in CCS against properties expressed by modal mu-calculus formulas. We demonstrate the applicability of our guidance mechanism by verifying several example protocols from XMC test-suite.
Protocol conversion problem involves identifying whether two or more protocols can be composed wi... more Protocol conversion problem involves identifying whether two or more protocols can be composed with or without an intermediary, referred to as a converter, to obtain a pre-specified desired behavior. We investigate this problem in formal setting and propose, for the first time, a temporal logic based automatic solution to the convertibility verification and synthesis. At its core, our technique is based on local model checking technique and determines the existence of the converter and if a converter exists, it is automatically synthesized. A number of key features of our technique distinguishes it from all existing formal and/or informal techniques. Firstly, we handle both data and control mismatches (for the first time), using a single unifying model checking based solution. Secondly, the proposed approach uses temporal logic for the specification of correct behaviors (unlike earlier automaton based specifications) which is both elegant and natural to express event ordering and data-matching requirements. Finally, we have have experimented extensively with the examples available in the existing literature to evaluate the applicability of our technique in wide range of applications.
Web services are fast emerging as the technology of choice to build distributed information syste... more Web services are fast emerging as the technology of choice to build distributed information systems in multiple domains including e-Business and e-Science. An important challenge is to develop methodologies and tools that enable (semi-) automatic composition of services by taking into account the functional, non-functional and behavioral requirements of the service developer. This paper presents the fundamental concepts and issues related to service composition and provides a representative sample of existing work proposed by the AI planning and formal methods communities to address some of the challenges in service composition. It also provides a brief introduction to an iterative and incremental technique for modeling composite Web services proposed by the authors.
Parameterized systems verication is a long-standing problem, where the challenge is to verify tha... more Parameterized systems verication is a long-standing problem, where the challenge is to verify that a property holds for all (innite) instances of the parameterized system. Existing techniques aim to reduce this problem to checking the properties on smaller systems with a bound on the parameter referred to as the cut-o such that if the property holds for system instances of size cut-o that implies that it holds for larger system instances. In most existing techniques, human guidance is required to deduce the invariants for the system's behavior, which are then used to compute cut-o. In contrast, we present an fully automatic sound method (but necessarily incomplete) for generating the cut-o that works for synchronous parameterized systems with heterogeneous processes communicating via single-cast and/or broadcast. Our technique is independent of the system topology and the property to be veried. Given the specication and the topology of the system, our technique generates the system-specic cut-o. We have realized our technique in a tool, Golok, which shows that it can be automated. We present the results of running Golok on 15 parameterized systems where we obtain smaller cut-os than those presented in the existing literature for 14 cases.
We study the problem of statistical model checking of probabilistic systems for PCTL unbounded un... more We study the problem of statistical model checking of probabilistic systems for PCTL unbounded until property P1p(ϕ1 U ϕ2) (where 1 ∈ {<, ≤, >, ≥}) using the computation of P ≤0 (ϕ 1 U ϕ 2 ). The approach is first proposed by Sen et al.
Let X = {X i } be a set of variables, each with a domain D i . An outcome α ∈ O is a complete ass... more Let X = {X i } be a set of variables, each with a domain D i . An outcome α ∈ O is a complete assignment to all the variables, denoted by the tuple α := α(X 1 ), α(X 2 ), . . . , α(X m ) such that α(X i ) ∈ D i for each X i ∈ X . The set of all possible outcomes is given by O = Xi∈X D i . We consider a preference language L for specifying: (a) unconditional intra-variable preferences ≻ i that are strict partial orders (i.e., irreflexive and transitive relations) over D i ; and (b) unconditional relative importance preferences that are strict partial orders over X .
Web services are software entities which provide a set of functionalities that can be accessed ov... more Web services are software entities which provide a set of functionalities that can be accessed over the Web. In general, the valuations of variables appearing in various functions provided by the service are not known before execution. Consequently, to analyze the behavior of a service, all possible valuations need to be considered, making the whole system infinite-state. Against this background, we propose a framework for modeling and composing Web services where desired (goal) and pre-existing (component) services exhibit infinite-state behavior. Our approach finitely represents such services using Symbolic Transition Systems (STSs) which are transition systems augmented with guards over infinitedomain variables. We develop a sound and complete logical approach for identifying the existence of composition of available component-STSs, such that the resulting composition is "simulated" by the goal-STS. In the event that the goal service cannot be realized from the existing components, our technique can also identify the cause for the failure and guide the user to achieve appropriate refinement of the goal specification, thereby paving the way for incremental development of composite services.
Recent advances in the field of intrusion detection brought new requirements to intrusion prevent... more Recent advances in the field of intrusion detection brought new requirements to intrusion prevention and response. Tra-ditionally, the response to the detected attack was selected and deployed manually, in the recent years the focus has shifted towards developing automated and semi-automated methodologies for responding to intrusions. In this context, the cost-sensitive intrusion response models have gained the most interest mainly due to their emphasis on the balance between potential damage incurred by the intrusion and cost of the response. However, one of the challenges in applying this approach is defining consistent and adaptable measure-ment of these cost factors on the basis of requirements and policy of the system being protected against intrusions. In this paper we present a structured methodology for eval-uating cost of responses based on three factors: the response operational cost associated with the daily maintenance of the response, the response goodness that measures...
Spread of infections (diseases, ideas, etc.) in a network can be modeled as the evolution of stat... more Spread of infections (diseases, ideas, etc.) in a network can be modeled as the evolution of states of nodes in a graph as a function of the states of their neighbors. Given an initial configuration of a network in which a subset of the nodes have been infected, and an infec- tion propagation function that specifies how the states of the nodes evolve over time, we show how to use model checking to identify, verify, and evaluate the effective- ness of intervention policies for containing the propaga- tion of infection over such networks.
We study a dominance relation for comparing outcomes based on unconditional qualitative preferenc... more We study a dominance relation for comparing outcomes based on unconditional qualitative preferences and compare it with its unconditional counterparts for TCP-nets and their variants. Dominance testing based on this relation can be carried out in polynomial time by evaluating the satisfiability of a logic formula.
Dominance testing, the problem of determining whether an outcome is preferred over another, is of... more Dominance testing, the problem of determining whether an outcome is preferred over another, is of fundamental importance in many applications. Hence, there is a need for algorithms and tools for dominance testing. CP-nets and TCP-nets are some of the widely studied languages for representing and reasoning with preferences. We reduce dominance testing in TCP-nets to reachability analysis in a graph of outcomes. We provide an encoding of TCP-nets in the form of a Kripke structure for CTL. We show how to compute dominance using NuSMV, a model checker for CTL. We present results of experiments that demonstrate the feasibility of our approach to dominance testing.
2012 Design, Automation & Test in Europe Conference & Exhibition (DATE), 2012
Systems-on-chip (SoCs) contain multiple interconnected and interacting components. In this paper,... more Systems-on-chip (SoCs) contain multiple interconnected and interacting components. In this paper, we present a compositional approach for the integration of multiple components with a wide range of protocol mismatches into a single SoC. We show how SoC construction can be done in single-step when all components are integrated at once or it can also be performed incrementally by adding components to an already integrated design. Using a number of AMBA IPs, we show that the proposed framework is able to perform protocol conversion in many cases where existing approaches fail.
2009 Design, Automation & Test in Europe Conference & Exhibition, 2009
The automated design of SoCs from pre-selected IPs that may require different clocks is challengi... more The automated design of SoCs from pre-selected IPs that may require different clocks is challenging because of the following issues. Firstly, protocol mismatches between IPs need to be resolved automatically before IPs are integrated. Secondly, the presence of multiple clocks makes the protocol conversion even more difficult. Thirdly, it is desirable that the resulting integration is correct-by-construction, i.e., the resulting SoC satisfies given system-level specifications. All of these issues have been studied extensively, although not in a unifying manner. In this paper we propose a framework based on protocol conversion that addresses all these issues. We have extensively studied many SoC design problems and show that the proposed methodology is capable of handling them better than other known approaches. A significant contribution of the proposed approach is that it nicely generalizes many existing techniques for formal SoC design and integrates them into a single approach.
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Papers by Samik Basu