138 research outputs found
Hardware-Assisted Secure Computation
The theory community has worked on Secure Multiparty Computation (SMC) for more than two decades, and has produced many protocols for many settings. One common thread in these works is that the protocols cannot use a Trusted Third Party (TTP), even though this is conceptually the simplest and most general solution. Thus, current protocols involve only the direct players---we call such protocols self-reliant. They often use blinded boolean circuits, which has several sources of overhead, some due to the circuit representation and some due to the blinding. However, secure coprocessors like the IBM 4758 have actual security properties similar to ideal TTPs. They also have little RAM and a slow CPU.We call such devices Tiny TTPs. The availability of real tiny TTPs opens the door for a different approach to SMC problems. One major challenge with this approach is how to execute large programs on large inputs using the small protected memory of a tiny TTP, while preserving the trust properties that an ideal TTP provides. In this thesis we have investigated the use of real TTPs to help with the solution of SMC problems. We start with the use of such TTPs to solve the Private Information Retrieval (PIR) problem, which is one important instance of SMC. Our implementation utilizes a 4758. The rest of the thesis is targeted at general SMC. Our SMC system, Faerieplay, moves some functionality into a tiny TTP, and thus avoids the blinded circuit overhead. Faerieplay consists of a compiler from high-level code to an arithmetic circuit with special gates for efficient indirect array access, and a virtual machine to execute this circuit on a tiny TTP while maintaining the typical SMC trust properties. We report on Faerieplay\u27s security properties, the specification of its components, and our implementation and experiments. These include comparisons with the Fairplay circuit-based two-party system, and an implementation of the Dijkstra graph shortest path algorithm. We also provide an implementation of an oblivious RAM which supports similar tiny TTP-based SMC functionality but using a standard RAM program. Performance comparisons show Faerieplay\u27s circuit approach to be considerably faster, at the expense of a more constrained programming environment when targeting a circuit
The halo mass function through the cosmic ages
In this paper we investigate how the halo mass function evolves with
redshift, based on a suite of very large (with N_p = 3072^3 - 6000^3 particles)
cosmological N-body simulations. Our halo catalogue data spans a redshift range
of z = 0-30, allowing us to probe the mass function from the dark ages to the
present. We utilise both the Friends-of-Friends (FOF) and Spherical Overdensity
(SO) halofinding methods to directly compare the mass function derived using
these commonly used halo definitions. The mass function from SO haloes exhibits
a clear evolution with redshift, especially during the recent era of dark
energy dominance (z < 1). We provide a redshift-parameterised fit for the SO
mass function valid for the entire redshift range to within ~20% as well as a
scheme to calculate the mass function for haloes with arbitrary overdensities.
The FOF mass function displays a weaker evolution with redshift. We provide a
`universal' fit for the FOF mass function, fitted to data across the entire
redshift range simultaneously, and observe redshift evolution in our data
versus this fit. The relative evolution of the mass functions derived via the
two methods is compared and we find that the mass functions most closely match
at z=0. The disparity at z=0 between the FOF and SO mass functions resides in
their high mass tails where the collapsed fraction of mass in SO haloes is ~80%
of that in FOF haloes. This difference grows with redshift so that, by z>20,
the SO algorithm finds a ~50-80% lower collapsed fraction in high mass haloes
than does the FOF algorithm, due in part to the significant over-linking
effects known to affect the FOF method.Comment: v4, 16 pages, 16 colour figures. Changed to match MNRAS print
version. NOTE: v1 of this paper has a typo in the fitting function. Please
ensure you use the latest versio
Programming-by-demonstration of reaching motions for robot grasping
Proceedings of: 14th International Conference on Advanced Robotics (ICAR 2009), 22-26 June 2009, Munich (Germany)This paper presents a novel approach to skill
modeling acquired from human demonstration. The approach
is based on fuzzy modeling and is using a planner for generating
corresponding robot trajectories. One of the main challenges
stems from the morphological differences between human and
robot hand/arm structure, which makes direct copying of human
motions impossible in the general case. Thus, the planner
works in hand state space, which is defined such that it is
perception-invariant and valid for both human and robot hand.
We show that this representation simplifies task reconstruction
and preserves the essential parts of the task as well as the
coordination between reaching and grasping motion. We also
show how our approach can generalize observed trajectories
based on multiple demonstrations and that the robot can match
a demonstrated behavoir, despite morphological differences.
To validate our approach we use a general-purpose robot
manipulator equipped with an anthropomorphic three-fingered
robot hand.European Community's Seventh Framework Progra
Apolarity, Hessian and Macaulay polynomials
A result by Macaulay states that an Artinian graded Gorenstein ring R of
socle dimension one and socle degree b can be realized as the apolar ring of a
homogeneous polynomial f of degree b. If R is the Jacobian ring of a smooth
hypersurface g=0, then b is just equal to the degree of the Hessian polynomial
of g. In this paper we investigate the relationship between f and the Hessian
polynomial of g.Comment: 12 pages. Improved exposition, minor correction
Perspective Chapter: Emotion Detection Using Speech Analysis and Deep Learning
Speech reflects the sentiment and emotions of humans. People can identify the emotional states in speech utterances, but there is a higher chance of perception error, which is generally termed as human error to identify the proper emotion when only using speech signals. Thus, artificial intelligence plays an important role in the detection of emotion through speech. Deep Learning is the subset of Machine Learning (ML) and artificial intelligence through which speech signal processing can be performed and the detection of emotions can be accomplished using speech. In this chapter, the classifiers of Machine Learning and Deep Learning will be reviewed. From the comparison in various studies and performances we will conclude what methods work better than others. We will discuss the limitations of these approaches as well. Accuracy scores will be discussed for each proposed system
Benefits and Security Challenges of Big Data Analytics
Big data analytics is a powerful technique used by companies to secure their data. However, data security remains a significant challenge for cultural entities such as libraries and museums, as hackers can target database systems and gain access to sensitive information. This study examines the benefits and security issues associated with big data analytics and proposes a manual approach for analyzing data with application to digital presentation and preservation of cultural heritage. By providing insights into the strengths and weaknesses of big data analytics and exploring strategies for securing data, the goal of the research is to help organizations make informed decisions about their data management practices
Small, Stupid, and Scalable: Secure Computing with Faerieplay *
ABSTRACT How can Agnes trust a computation C occurring at Boris's computer? In particular, how can Agnes can trust that C is occurring without Boris even being able to observe its internal state? One way is for Agnes to house C in a strong tamper-protected secure coprocessor at Boris's site. However, this approach is not scalable: neither in terms of computation-once C gets larger than the coprocessor, it becomes vulnerable to Boris again-nor in terms of cost. In this paper, we report on our Faerieplay project: rather than worrying about the limited size of a secure coprocessor, we try to make it as small as possible, with limited RAM and CPU. We start with the Fairplay work of Malkhi et al on implementing Yao's blinded-circuit solution to secure multiparty computation with software-this permits Agnes to trust C, but is too inefficient for all but small C. We then use our own prior work on using trusted third parties for practical Private Information Retrieval to design and prototype tiny trusted third parties (TTTPs) that substantially reduce the overhead involved in blind circuit evaluation
Reionization of the Milky Way, M31, and their satellites – I. Reionization history and star formation
Observations of the Milky Way (MW), M31, and their vicinity, known as the Local Group (LG), can provide clues about the sources of reionization. We present a suite of radiative transfer simulations based on initial conditions provided by the Constrained Local UniversE Simulations (CLUES) project that are designed to recreate the Local Universe, including a realistic MW–M31 pair and a nearby Virgo. Our box size (91Mpc) is large enough to incorporate the relevant sources of ionizing photons for the LG. We employ a range of source models, mimicking the potential effects of radiative feedback for dark matter haloes between ∼108 and 109M�. Although the LG mostly reionizes in an inside-out fashion, the final 40 per cent of its ionization shows some outside influence. For the LG satellites, we find no evidence that their redshift of reionization is related to the present-day mass of the satellite or the distance from the central galaxy. We find that fewer than 20 per cent of present-day satellites for MW and M31 have undergone any star formation prior to the end of global reionization. Approximately 5 per cent of these satellites could be classified as fossils,meaning the majority of star formation occurred at these early times. The more massive satellites have more cumulative star formation prior to the end of global reionization, but the scatter is significant, especially at the low-mass end. Present-day mass and distance from the central galaxy are poor predictors for the presence of ancient stellar populations in satellite galaxies
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