3,686 research outputs found
Chaotic Compilation for Encrypted Computing: Obfuscation but Not in Name
An `obfuscation' for encrypted computing is quantified exactly here, leading
to an argument that security against polynomial-time attacks has been achieved
for user data via the deliberately `chaotic' compilation required for security
properties in that environment. Encrypted computing is the emerging science and
technology of processors that take encrypted inputs to encrypted outputs via
encrypted intermediate values (at nearly conventional speeds). The aim is to
make user data in general-purpose computing secure against the operator and
operating system as potential adversaries. A stumbling block has always been
that memory addresses are data and good encryption means the encrypted value
varies randomly, and that makes hitting any target in memory problematic
without address decryption, yet decryption anywhere on the memory path would
open up many easily exploitable vulnerabilities. This paper `solves (chaotic)
compilation' for processors without address decryption, covering all of ANSI C
while satisfying the required security properties and opening up the field for
the standard software tool-chain and infrastructure. That produces the argument
referred to above, which may also hold without encryption.Comment: 31 pages. Version update adds "Chaotic" in title and throughout
paper, and recasts abstract and Intro and other sections of the text for
better access by cryptologists. To the same end it introduces the polynomial
time defense argument explicitly in the final section, having now set that
denouement out in the abstract and intr
Empirical Patterns in Google Scholar Citation Counts
Scholarly impact may be metricized using an author's total number of
citations as a stand-in for real worth, but this measure varies in
applicability between disciplines. The detail of the number of citations per
publication is nowadays mapped in much more detail on the Web, exposing certain
empirical patterns. This paper explores those patterns, using the citation data
from Google Scholar for a number of authors.Comment: 6 pages, 8 figures, submitted to Cyberpatterns 201
PT-symmetric quantum Liouvillian dynamics
We discuss a combination of unitary and anti-unitary symmetry of quantum
Liouvillian dynamics, in the context of open quantum systems, which implies a
D2 symmetry of the complex Liovillean spectrum. For sufficiently weak
system-bath coupling it implies a uniform decay rate for all coherences, i.e.
off-diagonal elements of the system's density matrix taken in the eigenbasis of
the Hamiltonian. As an example we discuss symmetrically boundary driven open
XXZ spin 1/2 chains.Comment: Note [18] added with respect to a published version, explaining the
symmetry of the matrix V [eq. (14)
Hierarchical social modularity in gorillas
Modern human societies show hierarchical social modularity (HSM) in which lower-order social units like nuclear families are nested inside increasingly larger units. It has been argued that this HSM evolved independently and after the chimpanzee–human split due to greater recognition of, and bonding between, dispersed kin. We used network modularity analysis and hierarchical clustering to quantify community structure within two western lowland gorilla populations. In both communities, we detected two hierarchically nested tiers of social structure which have not been previously quantified. Both tiers map closely to human social tiers. Genetic data from one population suggested that, as in humans, social unit membership was kin structured. The sizes of gorilla social units also showed the kind of consistent scaling ratio between social tiers observed in humans, baboons, toothed whales, and elephants. These results indicate that the hierarchical social organization observed in humans may have evolved far earlier than previously asserted and may not be a product of the social brain evolution unique to the hominin lineage
The simulation of coherent structures in a laminar boundary layer
Coherent structures in turbulent shear flows were studied extensively by several techniques, including the VITA technique which selects rapidly accelerating or decelerating regions in the flow. The evolution of a localized disturbance in a laminar boundary layer shows strong similarity to the evolution of coherent structures in a turbulent-wall bounded flow. Starting from a liftup-sweep motion, a strong shear layer develops which shares many of the features seen in conditionally-sampled turbulent velocity fields. The structure of the shear layer, Reynolds stress distribution, and wall pressure footprint are qualitatively the same, indicating that the dynamics responsible for the structure's evolution are simple mechanisms dependent only on the presence of a high mean shear and a wall and independent of the effects of local random fluctuations and outer flow effects. As the disturbance progressed, the development of streak-like-high- and low-speed regions associated with the three-dimensionality
Early Thermal Evolution of Planetesimals and its Impact on Processing and Dating of Meteoritic Material
Radioisotopic ages for meteorites and their components provide constraints on
the evolution of small bodies: timescales of accretion, thermal and aqueous
metamorphism, differentiation, cooling and impact metamorphism. Realising that
the decay heat of short-lived nuclides (e.g. 26Al, 60Fe), was the main heat
source driving differentiation and metamorphism, thermal modeling of small
bodies is of utmost importance to set individual meteorite age data into the
general context of the thermal evolution of their parent bodies, and to derive
general conclusions about the nature of planetary building blocks in the early
solar system. As a general result, modelling easily explains that iron
meteorites are older than chondrites, as early formed planetesimals experienced
a higher concentration of short-lived nuclides and more severe heating.
However, core formation processes may also extend to 10 Ma after formation of
Calcium-Aluminum-rich inclusions (CAIs). A general effect of the porous nature
of the starting material is that relatively small bodies (< few km) will also
differentiate if they form within 2 Ma after CAIs. A particular interesting
feature to be explored is the possibility that some chondrites may derive from
the outer undifferentiated layers of asteroids that are differentiated in their
interiors. This could explain the presence of remnant magnetization in some
chondrites due to a planetary magnetic field.Comment: 24 pages, 9 figures, Accepted for publication as a chapter in
Protostars and Planets VI, University of Arizona Press (2014), eds. H.
Beuther, R. Klessen, C. Dullemond, Th. Hennin
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