1,721,036 research outputs found
Agent control of cooperating satellites
No full textA novel, hybrid, agent architecture for (small)swarms of satellites has been developed. The software architecture for each satellite comprises ahigh-level rational agent linked to a low-level control system. The rational agent forms dynamicgoals, decides how to tackle them and passes theactual implementation of these plans to the control layer. The rational agent also has access to aMatLabmodel of the satellite dynamics, thus allowing it to carry out selective hypothetical reasoningabout potential options. This hybrid architecturehas been implemented on simulated Earth orbitingsatellites and hardware at Southampton’s satellitehardware simulation lab. While the deployment of satellites in formation within an Earth orbit is clearly both interesting and useful, this paper takes the spacecraft swarm further a?eld. In particular, we here investigate therational agent autonomy problem, including collision avoidance, fault diagnosis and recovery, and cooperative behaviour of such spacecraft deployed to explore groups of Trojan Asteroids
Computer-aided proof of Erdős discrepancy properties
Full text linkIn 1930s Paul Erdős conjectured that for any positive integer C in any infinite ±1 sequence (xn) there exists a subsequence xd, x2d, x3d, ..., xkd, for some positive integers k and d, such that |∑ki=1xi·d| >C. The conjecture has been referred to as one of the major open problems in combinatorial number theory and discrepancy theory. For the particular case of C = 1 a human proof of the conjecture exists; for C = 2 a bespoke computer program had generated sequences of length 1124 of discrepancy 2, but the status of the conjecture remained open even for such a small bound. We show that by encoding the problem into Boolean satisfiability and applying the state of the art SAT solvers, one can obtain a discrepancy 2 sequence of length 1160 and a proof of the Erdős discrepancy conjecture for C = 2, claiming that no discrepancy 2 sequence of length 1161, or more, exists. In the similar way, we obtain a precise bound of 127 645 on the maximal lengths of both multiplicative and completely multiplicative sequences of discrepancy 3. We also demonstrate that unrestricted discrepancy 3 sequences can be longer than 130 000
Reducing code complexity in hybrid control systems
No full textModern control systems are limited in their ability to react flexibly and autonomously to changing situations by the complexity inherent in analysing situations where many variables are present. We present an architecture based on a combination of agent languages and hybrid systems for managing high level decisions in such systems. A preliminary case study suggests that the complexity of the code of such a system increases much more slower in the face of increasing complexity of the underlying system, than in a more traditional approach based on finite state machines
Verification of programs via intermediate interpretation
Full text linkWe explore an approach to verification of programs via program transformation applied to an interpreter of a programming language. A specialization technique known as Turchin's supercompilation is used to specialize some interpreters with respect to the program models. We show that several safety properties of functional programs modeling a class of cache coherence protocols can be proved by a supercompiler and compare the results with our earlier work on direct verification via supercompilation not using intermediate interpretation. Our approach was in part inspired by an earlier work by E. De Angelis et al. (2014-2015) where verification via program transformation and intermediate interpretation was studied in the context of specialization of constraint logic programs. Keywords: program specialization, supercompilation, program analysis, program transformation, safety verification, cache coherence protocols
Querrying Encrypted Data in Graph Databases
Full text linkEncryption is an effective way to protect sensitive data in a database from various attacks. Querying encrypted data, however, becomes a challenge. Either the data should be decrypted before the querying, leaving it vulnerable to server-side attacks, or one has to apply computationally expensive methods for querying encrypted data. In this paper, we present a flexible mechanism for the execution of queries over encrypted graph databases. Data privacy is protected at the server side, through the use of multi-layered encryption and encryption layer adjustment, conducted dynamically during the execution of queries. The proposed scheme reveals less information to the adversary than in the case of static adjustment done prior to execution. We report on the implementation of the scheme as applied to a subset of Cypher graph queries (graph traversal queries) directed at a Neo4j graph database. The experimental results show the efficiency of query execution for various types of query on encrypted graph data stores
Satellite control using rational agent programming
No full textThe paper describes new techniques for agent based control of autonomous satellite operations. Associated control system technology, rational hybrid agents, agent programming, natural language programming for abstractions in sEnglish, English documents for agents, and a case study are presente
Online network intrusion detection system using temporal logic and stream data processing
No full textThese days, the world are becoming more interconnected, and the Internet has dominated the ways to communicate or to do business. Network security measures must be taken to protect the organization environment. Among these security measures are the intrusion detection systems. These systems aim to detect the actions that attempt to compromise the
confidentiality, availability, and integrity of a resource by monitoring the events occurring in computer systems and/or networks. The increasing amounts of data that are transmitted at higher and higher speed networks created a challenging problem for the current intrusion detection systems. Once the traffic exceeds the operational boundaries of these systems, packets are dropped. This means that some attacks will not be detected.
In this thesis, we propose developing an online network based intrusion detection system by the combined use of temporal logic and stream data processing. Temporal Logic formalisms allow us to represent attack patterns or normal behaviour. Stream data processing is a recent database technology applied to flows of data. It is designed with
high performance features for data intensive applications processing. In this work we develop a system where temporal logic specifications are automatically translated into stream queries that run on the stream database server and are continuously evaluated against the traffic to detect intrusions.
The experimental results show that this combination was efficient in using the resources of the running machines and was able to detect all the attacks in the test data.
Additionally, the proposed solution provides a concise and unambiguous way to formally represent attack signatures and it is extensible allowing attacks to be added. Also, it
is scalable as the system can benefit from using more CPUs and additional memory on the same machine, or using distributed servers
Querying Over Encrypted Databases and Flexible Access Control Using Advanced Encryption Adjustment Policies
No full textSecurity, especially data privacy, is a major barrier to using outsourced servers. Recent security breaches
have shown that a stronger protection mechanism is required to keep data private from curious administrators.
Prior efforts to address this security issue have been either unfeasibly slow or operationally limited. While
most protection efforts are focused on relational databases, additional security measures are still lacking.
However, the growing number of online users and the popularity of Web 2.0 have led to storage issues and
limitations of traditional relational databases, which have led to a preference for non-relational databases.
Non-relational databases lack security features, although there have been some basic attempts to address
confidentiality.
This thesis proposes the Secure Document DataBase (SDDB) framework, which uses a proxy to protect
outsourced databases and ensure user authentication and authorisation. This thesis’s framework is based on
the CryptDB concept and Ciphertext Policy Attributes-Based Encryption. This framework allows many users
to access a single data owner’s encrypted data in an outsourced document database. This is to protect an
outsourced database’s privacy from internal attacks (i.e., an honest-but-curious administrator) and external
attacks (i.e., unauthorised users) and ensures access control at the database level. A framework secures data
querying using multi-layer encryption and adjustment policies, resulting in three major novelties. First, under
multi-layer encryption, a new secure data querying method, Ciphertext Policy Attributes Based Encryption
(CP-ABE), has been used to validate database-level data access control. Second, under adjustment policies,
Release-Aware In-Out Encryption Adjustment (RAEA) has been developed to provide a trade-off between
security and performance during query execution. RAEA is a dynamic query execution technique for
conjunctive queries that adjusts in two directions: inward and outward adjustments. Third, under adjustment
policies, sorted criteria, and an update-aware adjustments policies are developed to address information
disclosed and communication rounds during query execution.
To achieve the thesis’s objective, we built a prototype on top of MongoDB that employs all adjustment
policies in JSON format to analyse performance and security. The proposed policies were tested using
datasets produced on either local or cloud-based database servers. The produced datasets were used to assess
the scalability of the proposed policies by examining the runtime as data size increased and database server
types. Security was measured by comparing the information revealed by the proposed policies with each
other and with that of simple encryption adjustment from related work. Performance was majorly measured
through runtime for i-iii terms: (i) decryption data for inward direction; (ii) re-encryption data for outward
direction; and (iii) communication between proxy and database. Security and performance were evaluated by
comparing the proposed policies with each other and to that of simple encryption adjustment through runtime
for i-iii terms and the information revealed for security. The evaluations indicated that, when compared to
simple adjustments, the proposed policies reduced execution time, reduced communication rounds, enhanced
performance, and ensured maximum security in terms of data leakage. They are effective for scalability data
and can be used with any relational or non-relational databases
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