Broadcast-enhanced key predistribution schemes

We present a formalisation of a category of schemes that we refer to as broadcast-enhanced key predistribution schemes (BEKPSs). These schemes are suitable for networks with access to a trusted base station and an authenticated broadcast channel. We demonstrate that the access to these extra resources allows for the creation of BEKPSs with advantages over key predistribution schemes such as flexibility and more efficient revocation. There are many possible ways to implement BEKPSs, and we propose a framework for describing and analysing them. In their paper “From Key Predistribution to Key Redistribution,” Cichoń et al. [2010] propose a scheme for “redistributing” keys to a wireless sensor network using a broadcast channel after an initial key predistribution. We classify this as a BEKPS and analyse it in that context. We provide simpler proofs of some results from their paper, give a precise analysis of the resilience of their scheme, and discuss possible modifications. We then study two scenarios where BEKPSs may be particularly desirable and propose a suitable family of BEKPSs for each case. We demonstrate that they are practical and efficient to implement, and our analysis shows their effectiveness in achieving suitable trade-offs between the conflicting priorities in resource-constrained networks

City government and urban inequalities

What potential do city governments have to prevent and mitigate worsening urban inequalities? Focusing on different urban scales of government, this discussion goes beyond the core tasks of urban service provision to consider strategies of: (i) distribution and deliberation (e.g. revenue measures, living wages or participatory budgeting); (ii) housing and planning (e.g. equity planning, inclusionary zoning, anti-displacement measures, social housing programmes); (iii) environment and infrastructure (e.g. water and waste services, mass transit and non-motorised transport alternatives); and (iv) urban citizenship (e.g. freedom of information, association and movement; public realm and open space strategies)

A Key Management Protocol for Multiphase Hierarchical Wireless Sensor Networks

The security of Wireless Sensor Networks (WSNs) has a direct reliance on secure and efficient key management. This leaves key management as a fundamental research topic in the field of WSNs security. Among the proposed key management schemes for WSNs security, LEAP (Localized Encryption and Authentication Protocol) has been regarded as an efficient protocol over the last years. LEAP supports the establishment of four types of keys. The security of these keys is under the assumption that the initial deployment phase is secure and the initial key is erased from sensor nodes after the initialization phase. However, the initial key is used again for node addition after the initialization phase whereas the new node can be compromised before erasing the key. A time-based key management scheme rethought the security of LEAP. We show the deficiency of the time-based key management scheme and proposed a key management scheme for multi-phase WSNs in this paper. The proposed scheme disperses the damage resulting from the disclosure of the initial key. We show it has better resilience and higher key connectivity probability through the analysis

A key management scheme for heterogeneous sensor networks using keyed-hash chain

We present a suite of key management scheme for heterogeneous sensor networks. In view of different types of communications, a single key can not satisfy various communication requirements. It is necessary to study the establishment and renewal of different types of keys in heterogeneous sensornetworks. In this paper, we propose a new key management scheme which can support five types of communications. Our basic scheme is based on a keyed-hash chain approach. A new cluster mechanism is used to improve the probability of key sharing between sensors and their cluster heads. Different from existing schemes where a node capture attack might lead to the disclosure of several key chains, our method can avoid this drawback through not storing network-wide generating keys inlow-cost sensors. Only pairwise keys involving the compromised node should be deleted in our scheme. It is motivated by the observation that all the information stored on a sensor may be disclosed once the sensor gets compromised. Through the analysis of both security and performance, we show the scheme meets the security requirements

A Key Predistribution Scheme for Sensor Networks Using Deployment Knowledge

To achieve security in wireless sensor networks, it is important to be able to encrypt messages sent among sensor nodes. Keys for encryption purposes must be agreed upon by communicating nodes. Due to resource constraints, achieving such key agreement in wireless sensor networks is nontrivial. Many key agreement schemes used in general networks, such as Diffie-Hellman and public-key-based schemes, are not suitable for wireless sensor networks. Predistribution of secret keys for all pairs of nodes is not viable due to the large amount of memory used when the network size is large. Recently, a random key predistribution scheme and its improvements have been proposed. A common assumption made by these random key predistribution schemes is that no deployment knowledge is available. Noticing that, in many practical scenarios, certain deployment knowledge may be available a priori, we propose a novel random key predistribution scheme that exploits deployment knowledge and avoids unnecessary key assignments. We show that the performance (including connectivity, memory usage, and network resilience against node capture) of sensor networks can be substantially improved with the use of our proposed scheme. The scheme and its detailed performance evaluation are presented in this paper

Multipath Key Establishment for Wireless Sensor Networks Using Just-Enough Redundancy Transmission

In random key predistribution techniques for wireless sensor networks, a relatively small number of keys are randomly chosen from a large key pool and are loaded on the sensors prior to deployment. After deployment, each sensor tries finding a common key shared by itself and each of its neighbors to establish a link key to protect the wireless communication between themselves. One intrinsic disadvantage of such techniques is that some neighboring sensors do not share any common key. In order to establish a link key among these neighbors, a multihop secure path may be used to deliver the secret. Unfortunately, the possibility of sensors being compromised on the path may render such an establishment process insecure. In this work, we propose and analyze the Just-Enough Redundancy Transmission (JERT) scheme that uses the powerful Maximum-Distance Separable (MDS) codes to address the problem. In the JERT scheme, the secret link key is encoded in (n, k) MDS code and transmitted through multiple multihop paths. To reduce the total information that needs to be transmitted, the redundant symbols of the MDS codes are transmitted only if the destination fails to decode the secret. The JERT scheme is demonstrated to be efficient and resilient against node capture. One salient feature of the JERT scheme is its flexibility of trading transmission for lower information disclosure

Wage Inequality in Rich Democracies : Policies and Politics

Økende økonomisk ulikhet er en betydelig utfordring for moderne avanserte demokratier. Økonomisk ulikhet skaper sosiale spenninger, reduserer sosial mobilitet, hindrer økonomisk vekst, og undergraver prinsippet om lik presentasjon som endelig kan utfordre demokratiske institusjoner. Denne doktorgradsavhandlingen undersøker hvordan demokratiske regjeringer kan anvende politiske verktøy til å redusere lønnsulikhet og politisk-ideologiske skillelinjer i bruk av slik politikk. Avhandlingen fokuserer særlig på lønnsulikhet ettersom dette er en sentral kilde til ulikheter i økonomiske muligheter og utfall. Lønnsulikhet angår størstedelen av befolkningen ettersom lønn er den dominerende inntektskilden. Gjennom tre artikler utforskes flere sider av økende lønnsulikhet. Først identifiseres de viktigste faktorene for økende lønnsulikhet. Deretter utforskes politiske tiltak som kan anvendes for å redusere lønnsulikhet. Endelig analyseres politisk-ideologiske aspekter i bruken av politiske tiltak mot lønnsulikhet. Den første artikkelen, «Bestemmelsesfaktorer for lønnsulikhet på tvers av demokratier», er den førte systematiske oversiktsartikkelen av kvantitative komparative empiriske studier av faktorer for lønnsulikhet på tvers av rike demokratier. Gjennom systematiske søk i tverrfaglige databaser ble 25 av 1965 identifiserte studier inkludert. Studiene utførte komparative analyser og innfridde kvalitetskriterier. Sentraliserte lønnsforhandlinger og høy dekning av kollektive avtaler bidro konsistent til lavere lønnsulikhet, mens store forskjeller i befolkningens kompetanse økte lønnsulikhet. Med utgangspunkt i disse studiene ble et empirisk informert teoretisk rammeverk utviklet for å bedre forstå faktorer som driver økende lønnsulikhet. Dette rammeverket er også nyttig for å veilede fremtidig forskning. Den andre artikkelen, «Hvilken offentlig politikk reduserer lønnsulikheter?», undersøker politiske tiltak for lønnsulikhet. Fokuset rettes spesielt mot politiske verktøy som direkte påvirker lave lønninger eller indirekte påvirker lave lønninger via arbeidstakere og arbeidsgiveres insentiver. Empiriske data ble innhentet og analysert for 29 rike demokratier. Resultatene viste nasjonal minstelønn, arbeidsbetingede stønader/ytelser («in-work benefits») og lovfestet stillingsvern er de mest relevante tiltakene for lønnsulikhet. Land med sjenerøs eller ingen lovfestet minstelønn har lavere lønnsulikhet, mens land med lav minstelønn har høyere lønnsulikhet. Land med sjenerøse arbeidsbetingede ytelser og strengt stillingsvern har høyere lønnsulikhet. For å bedre forstå politiske faktorer som skaper lønnsulikhet, fokuserer den tredje artikkelen på politisk-ideologiske skillelinjer i bruk av arbeidsbetingede stønader. Den tredje artikkelen, «Arbeidsbetingede stønader: (hvordan) spiller regjeringens ideologi en rolle?», medforfattet med Joan Abbas, bruker innsikter fra den andre artikkelen og undersøker politikken bak arbeidsbetingede stønader. Denne typen stønad er designet for å supplementere lave lønninger. Det var en mangel på studier av arbeidsbetingede stønader med et komparativt perspektiv. Studien undersøker hvordan regjeringers ideologiske orientering (venstre-/høyreorientert) påvirker bruken av arbeidsbetingede stønader basert på data for 30 rike demokratier i 2001-2013. Resultatene viser at arbeidsbetingede stønader inntar forskjellige institusjonelle former i ulike land, enten via skattesystemet eller mer tradisjonelle sosiale tiltak. Arbeidsbetingende stønader er hovedsakelig brukt av høyreorienterte regjeringer som også er mest tilbøyelig til å utvide denne typen stønad. Venstreorienterte regjeringer er derimot mindre tilbøyelig til å benytte og eventuelt ekspandere arbeidsbetingede stønader dersom det er en høy grad av kollektive lønnsforhandlinger som dekker mesteparten av den yrkesaktive befolkningen. Som sammenfatning bidrar avhandlingen på flere måter til eksisterende forskning på økonomisk ulikhet og velferdsstaten. Empirisk identifiseres sentrale faktorer for økte lønnsulikheter samt politiske tiltak som kan motvirke denne utviklingen. Disse funnene videreutvikles gjennom analyser som viser hvordan politisk kontekst former lønnsulikhet. Generelt bidrar venstreorienterte regjeringers politikk til reduserte lønnsulikheter, mens høyreorienterte regjeringers politikk bidrar til økte lønnsulikheter. Teoretisk bidrar avhandlingen med et teoretisk rammeverk for en mer nyansert forståelse av faktorer som øker lønnsulikhet. De nye teoretiske og empiriske innsiktene i denne avhandlingen kan informere fremtidig forskning og politikk. Samlet bidrar avhandlingen med kunnskap om mekanismer bak lønnsulikhet og identifiserer de mest effektive politiske tiltakene mot lønnsulikhet.Growing economic inequality is a major challenge for modern advanced democracies. Economic inequality creates social tensions, reduces social mobility, undermines equal representation and may ultimately challenge democratic institutions. This PhD dissertation examines how democratic governments can tackle economic inequality through policies that reduce wage inequalities and the underlying politics of these policies. The focus of this dissertation is specifically wage inequality, as this is a major component in inequality of economic opportunities and outcomes. After all, for most people wages are the dominant income source. Through three separate articles, this dissertation identifies the primary drivers of wage inequality, explores potential policy solutions, and analyses political aspects of applying policy measures for less wage inequality. The first article, “Determinants of wage inequality across advanced democracies”, represents the first systematic review of quantitative comparative studies of drivers of wage inequality across rich democracies. A systematic search in cross-disciplinary databases first yielded 1965 studies, of which, after closer screening, 25 were relevant and included in the further review. These studies comparatively analysed wage inequality and passed proposed quality assessment criteria. Centralised bargaining structure and high coverage of collective agreements consistently reduced wage inequality, while skill dispersion increased wage inequality. Based on these studies, I developed an empirically informed framework for understanding determinants of wage inequality that can also guide future research. The second article, “Which government policies reduce wage inequality?”, specifically examines policy instruments for wage inequality, as opposed to wider structural determinants such as collective bargaining and skill distribution. I focus on policy instruments that can impact low-wage employment directly or indirectly through workers' and employers' incentives for low pay. I collected and analysed data for 29 rich democracies and from 2001 to 2018. I find that countries with generous statutory minimum wage levels and countries without statutory minimum wages have lower wage inequality, in the latter case because they have well-functioning collective bargaining. Countries with low statutory minimum wages have higher wage inequality. Moreover, countries with generous in-work benefits and strict employment protections tend to have higher wage inequality. To better understand how political drivers shape wage inequality, the third article focusses on the politics behind in-work benefits. The article is entitled “In-work benefits: (how) does government partisanship matter?” and is co-authored with Joan Abbas. In-work benefits are meant to mitigate negative effects of low wages and thus reduce poverty and incentivise employment. However, there is a lack of studies on in-work benefits with cross-national perspectives. The article investigates how government partisanship (left-wing or right-wing) impacts levels of in-work benefits based on data for 30 rich democracies in 2001-2013. Results show that in-work benefits take on different institutional forms across countries, either through the tax system or more traditional social policies. Secondly, right-wing governments were more likely to expand these benefits. Contextual factors such as high collective bargaining coverage matter, as left-wing governments are less likely to use the policy when collective agreements cover most workers. In summary, this dissertation makes several important contributions to research on economic inequality and the welfare state. Empirically, this dissertation not only identifies the key drivers of wage inequality, but also the policies that are likely to reduce wage inequality. These findings are further developed through analyses showing how the political context shapes wage inequality. Generally, the policies left-wing governments implement reduce wage inequality, while the policies favoured by right-wing governments increase wage inequality. Theoretically, I present a framework for a nuanced understanding of drivers of wage inequality. These novel theoretical and empirical insights can inform future research and policies. Overall, this dissertation contributes with knowledge about the underlying mechanisms of wage inequality and the most effective policies to combat it.Doktorgradsavhandlin

Comments on a sensor network key redistribution technique of Cichon, Golebiewski and Kutylowski

Cichon, Golebiewski and Kutylowski (\cite{CGK}) proposed a technique for ``key redistribution\u27\u27 in sensor networks. The idea is that long-term keys held by the sensor nodes are used to encrypt temporal keys that a base station then broadcasts to the network. The temporal keys are used as session keys by the nodes in the sensor network. It is argued that this provides increased connectivity and resilience as compared to a standard Eschenauer-Gligor key predistribution scheme, as well as providing some additional advantages. In this paper, we provide some simpler proofs of some results from \cite{CGK}. As well, we give a precise analysis of the resilience of Cichon, Golebiewski and Kutylowski\u27s scheme, and we discuss modifications of the scheme based on defining a suitable intersection threshold

The politics of Piketty: what political science can learn from, and contribute to, the debate on Capital in the Twenty-First Century

Thomas Piketty's imposing volume has brought serious economics firmly into the mainstream of public debate on inequality, yet political science has been mostly absent from this debate. This article argues that political science has an essential contribution to make to this debate, and that Piketty's important and powerful book lacks a clear political theory. It develops this argument by first assessing and critiquing the changing nature of political science and its account of contemporary capitalism, and then suggesting how Piketty's thesis can be complemented, extended and challenged by focusing on the ways in which politics and collective action shape the economy and the distribution of income and wealth. Although Capital's principal message is that ‘capital is back’ and that without political interventions active political interventions will continue to grow, a political economy perspective would suggest another rather more fundamental critique: the very economic forces Piketty describes are embedded in institutional arrangements which can only be properly understood as political phenomena. In a sense capital itself – the central concept of the book – is almost meaningless without proper consideration of its political foundations. Even if the fact of capital accumulation may respond to an economic logic, the process is embedded in a very political logic. The examples of housing policy and the regulation, and failure to regulate, financial markets are used to illustrate these points