Prototype Implementation
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2022 ◽  
Author(s):  
giovanni bartolomeo

<p>We introduce a distributed, fine-granuled, policy-based resource access control protocol leveraging on Attribute-Based Encryption. The protocol secures the whole access control procedure from the authorization issuer to the resource server providing grant confidentiality, proof of possession, antiforgery and may be implemented through a common web token exchange flow plus a HTTP basic authentication. As such, it may easily map to Cloud computing SaaS paradigms, enabling services integration into a single authorization-centric ecosystem even across multiple identity domains. We also present the results of a performance evaluation on a first prototype implementation.</p>


Author(s):  
Sourav Das ◽  
Nitin Awathare ◽  
Ling Ren ◽  
Vinay J. Ribeiro ◽  
Umesh Bellur

Proof-of-Work (PoW) based blockchains typically allocate only a tiny fraction (e.g., less than 1% for Ethereum) of the average interarrival time (I) between blocks for validating smart contracts present in transactions. In such systems, block validation and PoW mining are typically performed sequentially, the former by CPUs and the latter by ASICs. A trivial increase in validation time (τ) introduces the popularly known Verifier's Dilemma, and as we demonstrate, causes more forking and hurts fairness. Large τ also reduces the tolerance for safety against a Byzantine adversary. Solutions that offload validation to a set of non-chain nodes (a.k.a. off-chain approaches) suffer from trust and performance issues that are non-trivial to resolve. In this paper, we present Tuxedo, the first on-chain protocol to theoretically scale τ/I ≈1 in PoW blockchains. The key innovation in Tuxedo is to perform CPU-based block processing in parallel to ASIC mining. We achieve this by allowing miners to delay validation of transactions in a block by up to ζ blocks, where ζ is a system parameter. We perform security analysis of Tuxedo considering all possible adversarial strategies in a synchronous network with maximum end-to-end delay Δ and demonstrate that Tuxedo achieves security equivalent to known results for longest chain PoW Nakamoto consensus. Our prototype implementation of Tuxedo atop Ethereum demonstrates that it can scale τ without suffering the harmful effects of naive scaling up of τ/I in existing blockchains


Machines ◽  
2021 ◽  
Vol 9 (12) ◽  
pp. 327
Author(s):  
Julio Garrido ◽  
Diego Silva ◽  
Juan Sáez

STEP-NC (Standard for the Exchange of Product Model Data–Numerical Control) for metal milling and turning is not implemented by industrial computer numerical controllers. Solutions reported are prototypes based on post-processing in G-code. Moreover, minority machining processes, such as stone cutting, have not yet been contemplated in the STEP-NC standard. This article takes that sector as a use case. An extended STEP-NC model for circular saw stone-cutting operations is proposed, and a prototype automation implementation is developed to work with this extended model. This article shows how modern technological resources for coordinated axes control provided by many industrial controllers for the automation of general-purpose machines can speed up the processes of implementing STEP-NC numerical controllers. This article proposes a mixed and flexible approach for STEP-NC-based machine automation, where different strategies can coexist when it comes to executing STEP-NC machining files, so controllers do not need to implement the standard in an exhaustive way for all the possible features, but only at selected ones when convenient. This is demonstrated in a prototype implementation which is able to process STEP-NC product files with mixed-feature types: standard milling and non-standard sawblade features for stone processing.


2021 ◽  
Author(s):  
giovanni bartolomeo

<p>We introduce a distributed, fine-granuled, policy-based resource access control protocol leveraging on Attribute-Based Encryption. The protocol secures the whole access control procedure from the authorization issuer to the resource server providing grant confidentiality, proof of possession, antiforgery and may be implemented through a common web token exchange flow plus a HTTP basic authentication. As such, it may easily map to Cloud computing SaaS paradigms, enabling services integration into a single authorization-centric ecosystem even across multiple identity domains. We also present the results of a performance evaluation on a first prototype implementation.</p>


2021 ◽  
Author(s):  
Bertrand Marchand ◽  
Yann Ponty ◽  
Laurent Bulteau

Abstract Hard graph problems are ubiquitous in Bioinformatics, inspiring the design of specialized Fixed-Parameter Tractable algorithms, many of which rely on a combination of tree-decomposition and dynamic programming. The time/space complexities of such approaches hinge critically on low values for the treewidth tw of the input graph. In order to extend their scope of applicability, we introduce the Tree-Diet problem, i.e. the removal of a minimal set of edges such that a given tree-decomposition can be slimmed down to a prescribed treewidth tw. Our rationale is that the time gained thanks to a smaller treewidth in a parameterized algorithm compensates the extra post-processing needed to take deleted edges into account. Our core result is an FPT dynamic programming algorithm for Tree-Diet, using 2^O(tw)n time and space. We complement this result with parameterized complexity lower-bounds for stronger variants (e.g., NP-hardness when tw or tw − tw is constant). We propose a prototype implementation for our approach which we apply on difficult instances of selected RNA-based problems: RNA design, sequence-structure alignment, and search of pseudoknotted RNAs in genomes, revealing very encouraging results. This work paves the way for a wider adoption of tree-decomposition-based algorithms in Bioinformatics.


2021 ◽  
Author(s):  
Kazuki Aiura ◽  
Takumasa Ishioka ◽  
Ryota Shiinay ◽  
Tatsuya Fukuiy ◽  
Tomohiro Taniguchiy ◽  
...  

2021 ◽  
Author(s):  
◽  
Neil Ramsay

<p>The development of computerised information systems for large scale emergency management is lacking. These systems could present information and support information transfer across shifts. This is important as providing timely information is critical for efficient search and rescue operations in an emergency environment. This thesis contributes the design and prototype implementation for an interactive visualisation, called RescueTime, which is then evaluated. The evaluation showed that RescueTime is as effective as a traditional tool used by emergency managers. This demonstrates the feasibility of designing and developing larger information systems, for the purpose of emergency management.</p>


2021 ◽  
Author(s):  
◽  
Neil Ramsay

<p>The development of computerised information systems for large scale emergency management is lacking. These systems could present information and support information transfer across shifts. This is important as providing timely information is critical for efficient search and rescue operations in an emergency environment. This thesis contributes the design and prototype implementation for an interactive visualisation, called RescueTime, which is then evaluated. The evaluation showed that RescueTime is as effective as a traditional tool used by emergency managers. This demonstrates the feasibility of designing and developing larger information systems, for the purpose of emergency management.</p>


2021 ◽  
Author(s):  
◽  
Ferry Hendrikx

<p>Since the earliest human communities, reputation has been used by people to decide whether they should trust and interact with someone else. Traditionally, reputation was established through a person’s standing, word of mouth and their associations. However, with the increasingly widespread use of the Internet, this situation has changed. In particular, all of the normal cues that help to build reputation are missing. Even the concept of identity is blurred by the common usage of pseudonyms.  In answer to this problem, many websites on the Internet have developed reputation systems that allow members to leave feedback about the performance of others in the execution of their duties. This accumulation of feedback about any individual can be used to characterise and predict their future behaviour in that context, allowing others to decide if they want to interact with that individual. Unfortunately, the information in each instance is limited to the narrow context of the website in which it was generated.  Not only is the reputation information constrained in context, it also limits the potential scope of what can be determined about an individual. The information that could be collected about entities includes social, demographic and reputation-based information. These are collectively called recommendation information in this thesis. Collecting this recommendation information from multiple sources and contexts should provide a wider view by which an entity can be evaluated than reputation alone could produce. The combination of these multiple sources of recommendation information can be naturally extended in the development of novel applications in areas such as access control and web service composition.  The GRAFT framework developed in this thesis encapsulates a paradigm shift in the way that reputation information is handled. It directly supports the collection and distribution goals by building a global distributed recommendation system that can be used to collect and make available recommendation information about both people and electronic services. This system can be used as both a drop-in replacement for existing systems, or it can be used to drive the consumption of recommendation information in novel new systems.  Recommendation information can be collected from both traditional reputation sources such as Amazon and eBay, and non-traditional reputation sources such as social networks, providing flexibility in what can be collected and subsequently utilised by consumers. The derivation of reputation information from non-reputation sources including demographic and social information, and the subsequent ability to use this recommendation information in the description and evaluation of policies is unique to GRAFT.  The major contributions of this thesis in the areas of reputation and reputation systems include the development of a reputation terminology, generalised models of reputation and reputation context, an extensive survey and taxonomy of reputation systems and a classification of existing reputation systems based on the taxonomy. This thesis also contributes an architecture for GRAFT, a prototype implementation of GRAFT showing its usefulness, and an evaluation that includes the results of a large number of simulation experiments showing how the architecture scales and handles both malicious peers and churn.</p>


2021 ◽  
Author(s):  
◽  
Ferry Hendrikx

<p>Since the earliest human communities, reputation has been used by people to decide whether they should trust and interact with someone else. Traditionally, reputation was established through a person’s standing, word of mouth and their associations. However, with the increasingly widespread use of the Internet, this situation has changed. In particular, all of the normal cues that help to build reputation are missing. Even the concept of identity is blurred by the common usage of pseudonyms.  In answer to this problem, many websites on the Internet have developed reputation systems that allow members to leave feedback about the performance of others in the execution of their duties. This accumulation of feedback about any individual can be used to characterise and predict their future behaviour in that context, allowing others to decide if they want to interact with that individual. Unfortunately, the information in each instance is limited to the narrow context of the website in which it was generated.  Not only is the reputation information constrained in context, it also limits the potential scope of what can be determined about an individual. The information that could be collected about entities includes social, demographic and reputation-based information. These are collectively called recommendation information in this thesis. Collecting this recommendation information from multiple sources and contexts should provide a wider view by which an entity can be evaluated than reputation alone could produce. The combination of these multiple sources of recommendation information can be naturally extended in the development of novel applications in areas such as access control and web service composition.  The GRAFT framework developed in this thesis encapsulates a paradigm shift in the way that reputation information is handled. It directly supports the collection and distribution goals by building a global distributed recommendation system that can be used to collect and make available recommendation information about both people and electronic services. This system can be used as both a drop-in replacement for existing systems, or it can be used to drive the consumption of recommendation information in novel new systems.  Recommendation information can be collected from both traditional reputation sources such as Amazon and eBay, and non-traditional reputation sources such as social networks, providing flexibility in what can be collected and subsequently utilised by consumers. The derivation of reputation information from non-reputation sources including demographic and social information, and the subsequent ability to use this recommendation information in the description and evaluation of policies is unique to GRAFT.  The major contributions of this thesis in the areas of reputation and reputation systems include the development of a reputation terminology, generalised models of reputation and reputation context, an extensive survey and taxonomy of reputation systems and a classification of existing reputation systems based on the taxonomy. This thesis also contributes an architecture for GRAFT, a prototype implementation of GRAFT showing its usefulness, and an evaluation that includes the results of a large number of simulation experiments showing how the architecture scales and handles both malicious peers and churn.</p>


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