State (computer science)

About: State (computer science) is a research topic. Over the lifetime, 24436 publications have been published within this topic receiving 225733 citations.

Microprocessor capable of stopping its operation at any cycle time

Abstract: Herein disclosed is a method of controlling a microprocessor in accordance with the present invention characterized in that, when the microprocessor for executing a microprogram in accordance with clock cycles Φ 1 and Φ 2 receives a command (i.e., STOP signal) for stopping a normal operation from the outside, a freezing signal (i.e., FRZ signal) synchronizing with the clock cycles is generated to bring the operation being executed into a stopped state.

Automated analysis of security protocols with global state

Abstract: Security APIs, key servers and protocols that need to keep the status of transactions, require to maintain a global, non-monotonic state, e.g., in the form of a database or register. However, most existing automated verification tools do not support the analysis of such stateful security protocols – sometimes because of fundamental reasons, such as the encoding of the protocol as Horn clauses, which are inherently monotonic. A notable exception is the recent tamarin prover which allows specifying protocols as multiset rewrite (msr) rules, a formalism expressive enough to encode state. As multiset rewriting is a " low-level " specification language with no direct support for concurrent message passing, encoding protocols correctly is a difficult and error-prone process. We propose a process calculus which is a variant of the applied pi calculus with constructs for manipulation of a global state by processes running in parallel. We show that this language can be translated to msr rules whilst preserving all security properties expressible in a dedicated first-order logic for security properties. The translation has been implemented in a prototype tool which uses the tamarin prover as a backend. We apply the tool to several case studies among which a simplified fragment of PKCS#11, the Yubikey security token, and an optimistic contract signing protocol.

Designing Trusted Embedded Systems from Finite State Machines

Abstract: Sequential components are crucial for a real-time embedded system as they control the system based on the system's current state and real life input. In this article, we explore the security and trust issues of sequential system design from the perspective of a finite state machine (FSM), which is the most popular model used to describe sequential systems. Specifically, we find that the traditional FSM synthesis procedure will introduce security risks and cannot guarantee trustworthiness in the implemented circuits. Indeed, we show that not only do there exist simple and effective ways to attack a sequential system, it is also possible to insert a hardware Trojan Horse into the design without introducing any significant design overhead. We then formally define the notion of trust in FSM and propose a novel approach to designing trusted circuits from the FSM specification. We demonstrate both our findings on the security threats and the effectiveness of our proposed method on Microelectronics Center of North Carolina (MCNC) sequential circuit benchmarks.

Analysis of the effect of program execution of calling components with data variable checkpointing and resource allocation analysis

Abstract: An error detection mechanism for detecting programming errors in a computer program A component of the computer program, eg, a procedure or function of the computer program, is analyzed to determine the effect of the component on resources used by the computer program A component is analyzed by traversing the computer instructions, ie, statements, of the component and tracking the state of resources used by the component as affected by the statements of the component Each resource has a prescribed behavior represented by a number of states and transition between states Violations in the prescribed behavior of a resource resulting from an emulated execution of the statements of the component are detected and reported as programming errors Resources used by two or more components are modelled by modelling externals of the components The effect of execution of a component on externals and resources of the component is determined by traversing one or more possible control flow paths through the component and tracking the use of each external and resource by each statement of each control flow path Once the effect of execution of a component on externals and resources of the component is determined, a model of the component is created and used to model externals and resources of other components which invoke the modelled component

Program Mode Switching

Abstract: A computing system is configured to execute a computer program on a server and to provide a video stream of the program output to a geographically remote client over a communication network. The computing system is further configured to provide executable content of the computer program to the client over the communication network in parallel with the video stream. When a sufficient amount of the executable content has been provided to the client execution of the computer program is transitioned from the server to the client. The transition optionally includes communicating a state of the computer program from the server to the client. The executable content can be provided to the client in an order that is determined based on the state of the computer program. Those parts of the executable content deemed most likely to be necessary to support game play on the client are given priority.