Geometric approach to Fletcher's ideal penalty function

Original article can be found at: www.springerlink.com Copyright Springer. [Originally produced as UH Technical Report 280, 1993]In this note, we derive a geometric formulation of an ideal penalty function for equality constrained problems. This differentiable penalty function requires no parameter estimation or adjustment, has numerical conditioning similar to that of the target function from which it is constructed, and also has the desirable property that the strict second-order constrained minima of the target function are precisely those strict second-order unconstrained minima of the penalty function which satisfy the constraints. Such a penalty function can be used to establish termination properties for algorithms which avoid ill-conditioned steps. Numerical values for the penalty function and its derivatives can be calculated efficiently using automatic differentiation techniques.Peer reviewe

Introduction : Virtually perfect security (transcript of discussion)

“Virtually Perfect Security” is an attempt to tie together three slightly different interlocking strands. The first is the fact that although we talk about security as if it were some sort of metaphysical property (so that a system is either secure or isn’t), we all know that really whether a system is secure or not depends on the context which you put it, and you can move a system to a different context and change whether it’s secure or not. In practice, we also usually prove security relative to a particular abstraction, and the danger is that we have a system that “really” is secure, and then we discover that the attacker is using a different abstraction. Our attempt to find abstractions which the attacker can’t fool with this trick with has pushed us into talking about security using abstractions that are further and further away from anything that a user might think of as comprehensible or convenien

A Note About the Semantics of Delegation

In many applications, mobile agents are used by a client to delegate a task. This task is usually performed by the agent on behalf of the client, by visiting various service provider's sites distributed over a network. This use of mobile agents raises many interesting security issues concerned with the trust relationships established through delegation mechanisms between client and agent, agent and service provider and client and service provider. In this paper we will explain why the traditional semantics of delegation used by existing access control mechanisms, either centralised or distributed, are generally not satisfactory to prevent and detect deception and why these problems are even more critical when these semantics are used in mobile agent paradigms.Non peer reviewe

Remote booting in a hostile world: to whom am I speaking? [Computer security]

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More security or less insecurity (transcript of discussion)

The purpose of this talk is to explore the possibility of an exploitable analogy between approaches to secure system design and theories of jurisprudence. The prevailing theory of jurisprudence in the West at the moment goes back to Hobbes. It was developed by Immanuel Kant and later by Rousseau, and is sometimes called the contractarian model after Rousseau’s idea of the social contract. It’s not the sort of contract that you look at and think, oh gosh, that might be nice, I might think about opting in to that, it’s more like a pop up licence agreement that says, do you want to comply with this contract, or would you rather be an outlaw. So you don’t get a lot of choice about it. Sometimes the same theory, flying the flag of Immanuel Kant, is called transcendental institutionalism, because the basic approach says, you identify the legal institutions that in a perfect world would govern society, and then you look at the processes and procedures, the protocols that everyone should follow in order to enable those institutions to work, and then you say, right, that can’t be transcended, so therefore there’s a moral imperative for everyone to do it. So this model doesn’t pay any attention to the actual society that emerges, or to the incentives that these processes actually place on various people to act in a particular way. It doesn’t look at any interaction effects, it simply says, well you have to behave in this particular way because that’s what the law says you have to do, and the law is the law, and anybody who doesn’t behave in that way is a criminal, or (in our terms) is an attackerFinal Accepted Versio

Analysis of DoS Attacks at MAC Layer in Mobile Adhoc Networks

—Wireless network security has received tremendous attention due to the vulnerabilities exposed in the open communication medium. The most common wireless Medium Access Control (MAC) protocol is IEEE 802.11, which assumes all the nodes in the network are cooperative. However, nodes may purposefully misbehave in order to disrupt network performance, obtain extra bandwidth and conserve resources. These MAC layer misbehaviours can lead to Denial of Service (DoS) attacks which can disrupt the network operation. There is a lack of comprehensive analysis of MAC layer misbehaviour driven DoS attacks for the IEEE 802.11 protocol. This research studied possible MAC layer DoS attack strategies that are driven by the MAC layer malicious/selfish nodes and investigates the performance of the IEEE 802.11 protocol. Such DoS attacks caused by malicious and selfish nodes violating backoff timers associated with the protocol. The experimental and analytical approach evaluates several practical MAC layer backoff value manipulation and the impact of such attacks on the network performance and stability in MANETs. The simulation results show that introducing DoS attacks at MAC layer could significantly affect the network throughput and data packet collision rate. This paper concludes that DoS attacks with selfish/malicious intend can obtain a larger throughput by denying well-behaved nodes to obtain deserved throughput, also DoS attacks with the intend of complete destruction of the network can succee

Modular design of data-parallel graph algorithms

Amorphous Data Parallelism has proven to be a suitable vehicle for implementing concurrent graph algorithms effectively on multi-core architectures. In view of the growing complexity of graph algorithms for information analysis, there is a need to facilitate modular design techniques in the context of Amorphous Data Parallelism. In this paper, we investigate what it takes to formulate algorithms possessing Amorphous Data Parallelism in a modular fashion enabling a large degree of code re-use. Using the betweenness centrality algorithm, a widely popular algorithm in the analysis of social networks, we demonstrate that a single optimisation technique can suffice to enable a modular programming style without loosing the efficiency of a tailor-made monolithic implementation