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

“This material is presented to ensure timely dissemination of scholarly and technical work. Copyright and all rights therein are retained by authors or by other copyright holders. All persons copying this information are expected to adhere to the terms and constraints invoked by each author's copyright. In most cases, these works may not be reposted without the explicit permission of the copyright holder." “Copyright IEEE. Personal use of this material is permitted. However, permission to reprint/republish this material for advertising or promotional purposes or for creating new collective works for resale or redistribution to servers or lists, or to reuse any copyrighted component of this work in other works must be obtained from the IEEE.”Today's networked computer systems are very vulnerable to attack: terminal software, like that used by the X Window System, is frequently passed across a network, and a trojan horse can easily be inserted while it is in transit. Many other software products, including operating systems, load parts of themselves from a server across a network. Although users may be confident that their workstation is physically secure, some part of the network to which they are attached almost certainly is not secure. Most proposals that recommend cryptographic means to protect remotely loaded software also eliminate the advantages of remote loading-for example, ease of reconfiguration, upgrade distribution, and maintenance. For this reason, they have largely been abandoned before finding their way into commercial products. The article shows that, contrary to intuition, it is no more difficult to protect a workstation that loads its software across an insecure network than to protect a stand-alone workstation. In contrast to prevailing practice, the authors make essential use of a collision-rich hash function to ensure that an exhaustive off-line search by the opponent will produce not one, but many candidate pass words. This strategy forces the opponent into an open, on-line guessing attack and offers the user a defensive strategy unavailable in the case of an off-line attack.Peer reviewe

Evidence for aggregation and export of cyanobacteria and nano-eukaryotes from the Sargasso Sea euphotic zone

Pico-plankton and nano-plankton are generally thought to represent a negligible fraction of the total particulate organic carbon (POC) export flux in oligotrophic gyres due to their small size, slow individual sinking rates, and tight grazer control that leads to high rates of recycling in the euphotic zone. Based upon recent inverse modeling and network analysis however, it has been hypothesized that pico-plankton, including the cyanobacteria <i>Synechococcus</i> and <i>Prochlorococcus</i>, and nano-plankton contribute significantly to POC export, via formation and gravitational settling of aggregates and/or consumption of those aggregates by mesozooplankton, in proportion to their contribution to net primary production. This study presents total suspended particulate (>0.7 μm) and particle size-fractionated (10–20 μm, 20–53 μm, >53 μm) pigment concentrations from within and below the euphotic zone in the oligotrophic subtropical North Atlantic, collected using Niskin bottles and large volume in-situ pumps, respectively. Results show the indicator pigments for <i>Synechococcus</i>, <i>Prochlorococcus</i> and nano-eukaryotes are; (1) found at depths down to 500 m, and; (2) essentially constant, relative to the sum of all indicator pigments, across particle size fractions ranging from 10 μm to >53 μm. Based upon the presence of chlorophyll precursor and degradation pigments, and that in situ pumps do not effectively sample fecal pellets, it is concluded that these pigments were redistributed to deeper waters on larger, more rapidly sinking aggregates likely by gravitational settling and/or convective mixing. Using available pigment and ancillary data from these cruises, these <i>Synechococcus, Prochlorococcus</i> and nano-plankton derived aggregates are estimated to contribute 2–13% (5 ± 4%), 1–20% (5 ± 7%), and 6–43% (23 ± 14%) of the total sediment trap POC flux measured on the same cruises, respectively. Furthermore, nano-eukaryotes contribute equally to POC export and autotrophic biomass, while cyanobacteria contributions to POC export are one-tenth of their contribution to autotrophic biomass. These field observations provide direct evidence that pico- and nano-plankton represent a significant contribution to the total POC export via formation of aggregates in this oligotrophic ocean gyre. We suggest that aggregate formation and fate should be included in ecosystem models, particularly as oligotrophic regions are hypothesized to expand in areal extent with warming and increased stratification in the future

Regularizing threshold priors with sparse response patterns in Bayesian factor analysis with categorical indicators

Using instruments comprising ordered responses to items are ubiquitous for studying many constructs of interest. However, using such an item response format may lead to items with response categories infrequently endorsed or unendorsed completely. In maximum likelihood estimation, this results in non-existing estimates for thresholds. This work focuses on a Bayesian estimation approach to counter this issue. The issue changes from the existence of an estimate to how to effectively construct threshold priors. The proposed prior specification reconceptualizes the threshold prior as prior on the probability of each response category. A metric that is easier to manipulate while maintaining the necessary ordering constraints on the thresholds. The resulting induced-prior is more communicable, and we demonstrate comparable statistical efficiency that existing threshold priors. Evidence is provided using a simulated data set, a Monte Carlo simulation study, and an example multi-group item-factor model analysis. All analyses demonstrate how at least a relatively informative threshold prior is necessary to avoid inefficient posterior sampling and increase confidence in the coverage rates of posterior credible intervals

Plankton community composition, organic carbon and thorium-234 particle size distributions, and particle export in the Sargasso Sea

Measurements of plankton community composition (eight planktonic groups), particle size-fractionated (10, 20, 53, 70, and 100-μm Nitex screens) distributions of organic carbon (OC) and 234Th, and particle export of OC and 234Th are reported over a seasonal cycle (2006–2007) from the Bermuda Atlantic Time-Series (BATS) site. Results indicate a convergence of the particle size distributions of OC and 234Th during the winter-spring bloom period (January–March, 2007). The observed convergence of these particle size distributions is directly correlated to the depth-integrated abundance of autotrophic pico-eukaryotes (r = 0.97, P \u3c 0.05) and, to a lesser extent, Synechococcus (r = 0.85, P \u3c 0.14). In addition, there are positive correlations between the sediment trap flux of OC and 234Th at 150 m and the depth-integrated abundance of pico-eukaryotes (r = 0.94, P \u3c 0.06 for OC, and r = 0.98, P \u3c 0.05 for 234Th) and Synechococcus (r = 0.95, P \u3c 0.05 for OC, and r = 0.94, P \u3c 0.06 for 234Th). An implication of these observations and recent modeling studies (Richardson and Jackson, 2007) is that, although small in size, pico-plankton may influence large particle export from the surface waters of the subtropical Atlantic

A latter day Judas? Security, diplomatic protection, and the Foreign Office Security Department, 1955 – 1987

This article looks at the response of the British Foreign Office to security threats to HMG diplomats and diplomatic posts, placing security at the heart of the study of UK diplomacy. It explores the response of the Foreign Office’s Security Department to the threat of espionage by hostile states, and the increasingly violent threats posed by terrorist groups and other non-state groups to diplomats and diplomatic premises overseas. It seeks to build on earlier work on the development of the Security Department, suggesting that security within the Foreign Office was taken increasingly seriously as the lives of officials came under threat. It also looks at the broader role that security plays in diplomacy, and the tensions between public diplomacy and the protection of officials serving overseas

Non-invasive testing for liver pathology in alpha-1 antitrypsin deficiency

BACKGROUND: Many patients with alpha-1 antitrypsin deficiency (A1ATD) receive care in respiratory clinics without access to specialist hepatology expertise. Liver disease can develop asymptomatically, and non-invasive markers of fibrosis may help identify patients who require definitive assessment with liver biopsy. We evaluated the utility of non-invasive markers of liver fibrosis in A1ATD to guide testing in settings without ready access to hepatology expertise. METHODS: Patients attending the London A1ATD service undergo assessment using blood tests to calculate the 'APRI' and 'FIB-4' score, liver ultrasound and Fibroscan. Liver biopsy is offered to patients who have abnormal liver function tests with abnormal liver ultrasound and/or liver stiffness >6 kPa on Fibroscan. Liver biopsies were assessed for the presence of A1AT, steatosis, fibrosis and inflammation. RESULTS: 75 patients with A1ATD had results for analysis, 56% were female, age 16-82 years. 75% of patients had Fibroscan 8 kPa. There was a significant correlation between FIB-4 and Fibroscan (r=0.244, p=0.035). Fibroscan >6 kPa corresponded to a FIB-4 score of >1.26. However, FIB-4 >1.26 had poor sensitivity (47%), specificity (32%) and positive-predictive value (PPV; 36%) to identify Fibroscan >6 kPa. The negative-predictive value (NPV) was stronger at 81%. APRI data were similar. Twelve patients underwent liver biopsy, with 11 reports available for analysis. Six had FIB-4 scores<1.26 and five had Fibroscan of <6 kPa. A1AT was present in 64% of biopsies, steatosis in 82%, mild fibrosis in 36%, moderate fibrosis in 9% and severe fibrosis in 9%. CONCLUSION: A combination of liver ultrasound and non-invasive fibrosis tests can help identify patients with A1ATD liver injury. However, APRI and FIB-4 scores alone had poor sensitivity and specificity to justify use as an independent tool for liver pathology in A1ATD

Estimates of Micro-, Nano-, and Picoplankton Contributions to Particle Export in the Northeast Pacific

The contributions of micro-, nano-, and picoplankton to particle export were estimated from measurements of size-fractionated particulate 234Th, organic carbon, and phytoplankton indicator pigments obtained during five cruises between 2010 and 2012 along Line P in the subarctic northeast Pacific Ocean. Sinking fluxes of particulate organic carbon (POC) and indicator pigments were calculated from 234Th–238U disequilibria and, during two cruises, measured by sediment trap at Ocean Station Papa. POC fluxes at 100 m ranged from 0.65–7.95 mmol m−2 d−1, similar in magnitude to previous results at Line P. Microplankton pigments dominate indicator pigment fluxes (averaging 69 ± 19% of total pigment flux), while nanoplankton pigments comprised the majority of pigment standing stocks (averaging 64 ± 23% of total pigment standing stock). Indicator pigment loss rates (the ratio of pigment export flux to pigment standing stock) point to preferential export of larger microplankton relative to smaller nano- and picoplankton. However, indicator pigments do not quantitatively trace particle export resulting from zooplankton grazing, which may be an important pathway for the export of small phytoplankton. These results have important implications for understanding the magnitude and mechanisms controlling the biological pump at Line P in particular, and more generally in oligotrophic gyres and high-nutrient, low-chlorophyll regions where small phytoplankton represent a major component of the autotrophic community

Pico without public keys

This document is the Accepted Manuscript version of the following paper: Frank Stajano, Bruce Christianson, Mark Lomas, Graeme Jenkinson, Jeunese Payne, Max Spencer, and Quentin Stafford Fraser, 'Pico without Public Keys', Security Protocols XXIII, 23rd International Workshop Cambridge, March 31- April 2, 2015, Revised Selected Papers, pp. 195-211, part of the Lecture Notes in Computer Science book series (LNCS, Vol. 9379), first online 25 November 2015, ISBN: 978-3-319-26095-2. The final publication is available at Springer via: https://link.springer.com/chapter/10.1007%2F978-3-319-26096-9_21v.Pico is a user authentication system that does not require remembering secrets. It is based on a personal handheld token that holds the user’s credentials and that is unlocked by a “personal aura” generated by digital accessories worn by the owner. The token, acting as prover, engages in a public-key-based authentication protocol with the verifier. What would happen to Pico if success of the mythical quantum computer meant secure public key primitives were no longer available, or if for other reasons such as energy consumption we preferred not to deploy them? More generally, what would happen under those circumstances to user authentication on the web, which relies heavily on public key cryptography through HTTPS/TLS? Although the symmetric-key-vs-public-key debate dates back to the 1990s, we note that the problematic aspects of public key deployment that were identified back then are still ubiquitous today. In particular, although public key cryptography is widely deployed on the web, revocation still doesn’t work. We discuss ways of providing desirable properties of public-key-based user authentication systems using symmetric-key primitives and tamperevident tokens. In particular, we present a protocol through which a compromise of the user credentials file at one website does not require users to change their credentials at that website or any other. We also note that the current prototype of Pico, when working in compatibility mode through the Pico Lens (i.e. with websites that are unaware of the Pico protocols), doesn’t actually use public key cryptography, other than that implicit in TLS. With minor tweaks we adopt this as the native mode for Pico, dropping public key cryptography and achieving much greater deployability without any noteworthy loss in security

Management of coastal dunes affected by shrub encroachment: are rabbits an ally or an enemy of restoration?

In coastal dunes, shrub encroachment disrupts natural disturbance, and reduces habitat heterogeneity and species composition. In this paper, we implemented a pilot scale trial aimed at restoring coastal dunes affected by the encroachment by the shrub Retama monosperma (hereinafter Retama) as well as strengthening the populations of Thymus carnosus (regionally cataloged as ‘Critically Endangered’). A total 3 ha of Retama shrub was clearcut in two sites with different Retama cover (54 and 72%). The effect of rabbits on vegetation recovery was assessed by placing exclosures both in treated and untreated plots in Spring, 2015. Plant composition, species richness and diversity were evaluated two years after treatments (with and without Retama clearing, and with and without rabbit exclusion). Retama clearing alone did not allow the recovery of plant composition typical of gray dunes two-years after treatments, but resulted in a biodiversity loss within the Retama understorey when rabbits were present. However, Retama clearing resulted in a significant vigor improvement of T. carnosus in the site with the highest density of Retama. Rabbit exclusion significantly increased species richness and Shannon-Wiener diversity index, and allowed the recovery of plant composition typical of gray dunes. The results suggest that shrub encroachment caused by Retama has a long-lasting negative impact on dune vegetation and that periodic clearing should be combined with rabbit exclusion at least during early restoration stages of dune vegetation. To recover the population of T. carnosus, Retama should be prevented from reaching high cover and periodic clearing without rabbit exclusion is suggested

Using MODIS to detect cropping frequency variation in mechanized agriculture in Amazonia.

Policy makers concerned with managing rapidly developing agriculture on the Amazon frontier currently have no Basin-wide spatial and temporal information on exactly when and how soubean and other mechanized annual cropping have developed in the region. To address this, we present a reliminary evaluation of the use of moderate resolution Imaging Spectroradiometer (MODIS) 250 m vegetation index (VI) time-series data to detect croppping frequency in two municipalities, Vilhena, Rondônia, and Santarém, Pará