Breaking ‘128-bit Secure’ Supersingular Binary Curves

In late 2012 and early 2013 the discrete logarithm problem (DLP) in finite fields of small characteristic underwent a dramatic series of breakthroughs, culminating in a heuristic quasi-polynomial time algorithm, due to Barbulescu, Gaudry, Joux and Thomé. Using these developments, Adj, Menezes, Oliveira and Rodríguez-Henríquez analysed the concrete security of the DLP, as it arises from pairings on (the Jacobians of) various genus one and two supersingular curves in the literature, which were originally thought to be 128-bit secure. In particular, they suggested that the new algorithms have no impact on the security of a genus one curve over F21223 , and reduce the security of a genus two curve over F2367 to 94.6 bits. In this paper we propose a new field representation and efficient general descent principles which together make the new techniques far more practical. Indeed, at the ‘128-bit security level’ our analysis shows that the aforementioned genus one curve has approximately 59 bits of security, and we report a total break of the genus two curv

Biological nitrate transport in sediments on the Peruvian margin mitigates benthic sulfide emissions and drives pelagic N loss during stagnation events

Highlights • Very high rates of dissimilatory nitrate reduction to ammonium by Thioploca. • Non-steady state model predicts Thioploca survival on intracellular nitrate reservoir. • Ammonium release by Thioploca may be coupled to pelagic N loss by anammox. • Thioploca may contribute to anammox long after bottom water nitrate disappearance. • Model indicates that benthic foraminifera account for 90% of benthic N2 production. Abstract Benthic N cycling in the Peruvian oxygen minimum zone (OMZ) was investigated at ten stations along 12oS from the middle shelf (74 m) to the upper slope (1024 m) using in situ flux measurements, sediment biogeochemistry and modelling. Middle shelf sediments were covered by mats of the filamentous bacteria Thioploca spp. and contained a large ‘hidden’ pool of nitrate that was not detectable in the porewater. This was attributed to a biological nitrate reservoir stored within the bacteria to oxidize sulfide to sulfate during ‘dissimilatory nitrate reduction to ammonium’ (DNRA). The extremely high rates of DNRA on the shelf (15.6 mmol m-2 d-1 of N), determined using an empirical steady-state model, could easily supply all the ammonium requirements for anammox in the water column. The model further showed that denitrification by foraminifera may account for 90% of N2 production at the lower edge of the OMZ. At the time of sampling, dissolved oxygen was below detection limit down to 400 m and the water body overlying the shelf had stagnated, resulting in complete depletion of nitrate and nitrite. A decrease in the biological nitrate pool was observed on the shelf during fieldwork concomitant with a rise in porewater sulfide levels in surface sediments to 2 mM. Using a non-steady state model to simulate this natural anoxia experiment, these observations were shown to be consistent with Thioploca surviving on a dwindling intracellular nitrate reservoir to survive the stagnation period. The model shows that sediments hosting Thioploca are able to maintain high ammonium fluxes for many weeks following stagnation, potentially sustaining pelagic N loss by anammox. In contrast, sulfide emissions remain low, reducing the economic risk to the Peruvian fishery by toxic sulfide plume development

Strategic marketing in the NHS:Kwik-health NHS Trust

Unlike managers in most service organizations, hospital managers do not have significant control over the shape or cost of the service product or the manner of its delivery. Hence, the crucial issue for hospital management to address is how to develop the marketing of a service the control of which is divorced from those with the strategic market perspective. While the internal management of hospital care in NHS is in its infancy, initial developments such as clinical directorates point the way forward in creating a market orientation within provider units. Ultimately, it must be considered what degree of influence over clinical decisions affecting hospital services is realistic, ethical and desirable for strategic marketing and business services. Arguably there is a case for the adoption of some middle ground, with both sides moving from their present positions but perhaps with the clinicians moving furthest

Developing a market orientation in the Health Service: a survey of acute NHS Trusts in Scotland

Argues that the introduction of the quasi market mechanism into the Health Service has required that managers within NHS trusts acquire new managerial skills relating to market operations and, more importantly, reorientate their organizations towards the marketplace. Examines the pattern of development which has occurred within acute trusts across Scotland in the past three years, and argues that managers in the majority of trusts have developed a remarkably robust and relevant conceptualization of the nature and application of marketing within the NHS, reflecting the difficulties managers have faced in selling the concept of marketing to a generally sceptical body of clinicians. Notes, in part owing to such professional scepticism, that the development of marketing as an implementable approach to operations has lagged significantly behind the managerial conceptualization, although this cannot be attributed solely to resistance from clinicians and other health care professionals. Rather, suggests that such limited progress in implementing a market orientation reflects a range of "structural" barriers, both within individual trusts and the specific market environment faced by trusts

Uncertainties surrounding natural rate estimates in the G7

It is four decades since Phelps (1967) and Friedman (1968) unveiled the natural rate of unemployment hypothesis, and the concept of an equilibrium rate of unemployment is central to the prevailing theories of labour market behaviour and the relationship between unemployment and inflation. Moreover, the natural rate and associated unemployment gaps are seen as important reference points, typically as part of a broad range of indicators, by policy makers who need to assess short-term inflation developments and/or consider appropriate decompositions of fiscal balances into their structural and cyclical components. Yet, as surveys and symposia have illustrated (Bean 1994, Cross 1995, Journal of Economic Perspectives 1997), there remains much uncertainty both about which factors do and do not determine equilibrium rates of unemployment, and about the corresponding numerical values

Statistically hiding sets

Zero-knowledge set is a primitive introduced by Micali, Rabin, and Kilian (FOCS 2003) which enables a prover to commit a set to a verifier, without revealing even the size of the set. Later the prover can give zero-knowledge proofs to convince the verifier of membership/nonmembership of elements in/not in the committed set. We present a new primitive called Statistically Hiding Sets (SHS), similar to zero-knowledge sets, but providing an information theoretic hiding guarantee, rather than one based on efficient simulation. This is comparable to relaxing zero-knowledge proofs to witness independent proofs. More precisely, we continue to use the simulation paradigm for our definition, but do not require the simulator (nor the distinguisher) to be efficient. We present a new scheme for statistically hiding sets, which does not fit into the “Merkletree/mercurial-commitment” paradigm that has been used for all zero-knowledge set constructions so far. This not only provides efficiency gains compared to the best schemes in that paradigm, but also lets us provide statistical hiding; previous approaches required the prover to maintain growing amounts of state with each new proof for this