19 research outputs found
Public Evidence from Secret Ballots
Elections seem simple---aren't they just counting? But they have a unique,
challenging combination of security and privacy requirements. The stakes are
high; the context is adversarial; the electorate needs to be convinced that the
results are correct; and the secrecy of the ballot must be ensured. And they
have practical constraints: time is of the essence, and voting systems need to
be affordable and maintainable, and usable by voters, election officials, and
pollworkers. It is thus not surprising that voting is a rich research area
spanning theory, applied cryptography, practical systems analysis, usable
security, and statistics. Election integrity involves two key concepts:
convincing evidence that outcomes are correct and privacy, which amounts to
convincing assurance that there is no evidence about how any given person
voted. These are obviously in tension. We examine how current systems walk this
tightrope.Comment: To appear in E-Vote-Id '1
Evolution of Multidrug Resistance during Staphylococcus aureus Infection Involves Mutation of the Essential Two Component Regulator WalKR
Antimicrobial resistance in Staphylococcus aureus is a major public health threat, compounded by emergence of strains with resistance to vancomycin and daptomycin, both last line antimicrobials. Here we have performed high throughput DNA sequencing and comparative genomics for five clinical pairs of vancomycin-susceptible (VSSA) and vancomycin-intermediate ST239 S. aureus (VISA); each pair isolated before and after vancomycin treatment failure. These comparisons revealed a frequent pattern of mutation among the VISA strains within the essential walKR two-component regulatory locus involved in control of cell wall metabolism. We then conducted bi-directional allelic exchange experiments in our clinical VSSA and VISA strains and showed that single nucleotide substitutions within either walK or walR lead to co-resistance to vancomycin and daptomycin, and caused the typical cell wall thickening observed in resistant clinical isolates. Ion Torrent genome sequencing confirmed no additional regulatory mutations had been introduced into either the walR or walK VISA mutants during the allelic exchange process. However, two potential compensatory mutations were detected within putative transport genes for the walK mutant. The minimal genetic changes in either walK or walR also attenuated virulence, reduced biofilm formation, and led to consistent transcriptional changes that suggest an important role for this regulator in control of central metabolism. This study highlights the dramatic impacts of single mutations that arise during persistent S. aureus infections and demonstrates the role played by walKR to increase drug resistance, control metabolism and alter the virulence potential of this pathogen
Risk-Limiting Tallies
Many voter-verifiable, coercion-resistant schemes have been proposed, but
even the most carefully designed systems necessarily leak information via the
announced result. In corner cases, this may be problematic. For example, if all
the votes go to one candidate then all vote privacy evaporates. The mere
possibility of candidates getting no or few votes could have implications for
security in practice: if a coercer demands that a voter cast a vote for such an
unpopular candidate, then the voter may feel obliged to obey, even if she is
confident that the voting system satisfies the standard coercion resistance
definitions. With complex ballots, there may also be a danger of "Italian"
style (aka "signature") attacks: the coercer demands the voter cast a ballot
with a specific, identifying pattern. Here we propose an approach to tallying
end-to-end verifiable schemes that avoids revealing all the votes but still
achieves whatever confidence level in the announced result is desired. Now a
coerced voter can claim that the required vote must be amongst those that
remained shrouded. Our approach is based on the well-established notion of
Risk-Limiting Audits, but here applied to the tally rather than to the audit.
We show that this approach counters coercion threats arising in extreme tallies
and "Italian" attacks. We illustrate our approach by applying it to the Selene
scheme, and we extend the approach to Risk-Limiting Verification, where not all
vote trackers are revealed, thereby enhancing the coercion mitigation
properties of Selene
Use of inorganic wastes as immobilizing agents for soluble P in green waste-based composts
The study examines the effectiveness of red mud, blast furnace (BF) slag, and alum-derived water treatment sludge as immobilizing agents for excessive soluble P that had accumulated in three green waste-based composts.The three wastes were applied at 0%, 5%, 10%, and 20% w/w to three different composts, all containing extremely high concentrations of extractable P, and were incubated for 60 days. Water-soluble P was measured regularly throughout the incubation period, and at the end, P extractable with resin, 0.05 M NaHCO(3), and 0.005 M H(2)SO(4) were also measured.In the water extracts, inorganic P made up more than 85% of the total P present. All three materials had the ability to adsorb P and thus lowered water-soluble P concentrations. Water treatment sludge was clearly the most effective material, and this was attributed to its amorphous nature (thus, large Brunauer-Emmett-Teller surface area) and its acid pH (6.8) compared with the alkaline pH (10-11) of the other two materials. Water treatment sludge was also the most effective at lowering resin- and NaHCO(3)-extractable P. When H(2)SO(4) was used as the extractant, BF slag tended to be the most effective material at lowering extractable P, followed by water treatment sludge, and red mud. That is, the P immobilized by water treatment sludge was extractable with acid but not with water, resin, or NaHCO(3).Water treatment sludge has the potential to be used as an effective immobilizing agent for soluble P in composts, and it should be trialed under field conditions