Memory Erasability Amplification

Erasable memory is an important resource for designing practical cryptographic protocols that are secure against adaptive attacks. Many practical memory devices such as solid state drives, hard disks, or file systems are not perfectly erasable because a deletion operation leaves traces of the deleted data in the system. A number of methods for constructing a large erasable memory from a small one, e.g., using encryption, have been proposed. Despite the importance of erasable memory in cryptography, no formal model has been proposed that allows one to formally analyse such memory constructions or cryptographic protocols relying on erasable memory. The contribution of this paper is three-fold. First, we provide a formal model of erasable memory. A memory device allows a user to store, retrieve, and delete data, and it is characterised by a leakage function defining the extent to which erased data is still accessible to an adversary. Second, we investigate how the erasability of such memories can be amplified. We provide a number of constructions of memories with strong erasability guarantees from memories with weaker guarantees. One of these constructions of perfectly erasable memories from imperfectly erasable ones can be considered as the prototypical application of Canetti et al.\u27s All-or-Nothing Transform (AoNT). Motivated by this construction, we propose some new and better AoNTs that are either perfectly or computationally secure. These AoNTs are of possible independent interest. Third, we show (in the constructive cryptography framework) how the construction of erasable memory and its use in cryptographic protocols (for example to achieve adaptive security) can naturally be composed to obtain provable security of the overall protocol

Survey on securing data storage in the cloud

Cloud Computing has become a well-known primitive nowadays; many researchers and companies are embracing this fascinating technology with feverish haste. In the meantime, security and privacy challenges are brought forward while the number of cloud storage user increases expeditiously. In this work, we conduct an in-depth survey on recent research activities of cloud storage security in association with cloud computing. After an overview of the cloud storage system and its security problem, we focus on the key security requirement triad, i.e., data integrity, data confidentiality, and availability. For each of the three security objectives, we discuss the new unique challenges faced by the cloud storage services, summarize key issues discussed in the current literature, examine, and compare the existing and emerging approaches proposed to meet those new challenges, and point out possible extensions and futuristic research opportunities. The goal of our paper is to provide a state-of-the-art knowledge to new researchers who would like to join this exciting new field

Optical and thermal properties of samarium-doped fluorophosphate and fluoroaluminate glasses for high-dose, high-resolution dosimetry applications

Microbeam radiation therapy (MRT) is an experimental form of radiation treatment which causes less damage to normal tissue in comparison with customary broad-beam radiation treatment. In this method the synchrotron generated X-ray beam is passed through a multislit collimator and applied to the tumor in the form of an array of planar microbeams. MRT dosimetry is an extremely challenging task and no current detector can provide the required wide dynamic rang and high spatial resolution. In this thesis, fluorophosphate (FP) and fluoroaluminate (FA) glass plates doped with trivalent samarium (Sm3+) are characterized towards developing a potential X-ray detector suitable for MRT dosimetry. The detection is based on the difference in the photoluminescence signatures of Sm3+ ions and Sm2+ ions; the latter are formed under X-ray irradiation. This valency conversion is accompanied by the formation of defects including hole centers (HCs) and electron centers (ECs) in the glass structure which absorb light in the UV and visible regions (induced absorbance). Both FP and FA glasses show promising dynamic range for MRT and may be used as a linear sensor up to ~150 Gy and as a nonlinear sensor up to ∼2400 Gy, where saturation is reached. X-ray induced defects saturate at the same dose. The optimum doping concentration is in the 0.001˗ 0.2 at.% range. Doping with higher concentrations will decrease the conversion efficiency. The glass plates also show a very promising spatial resolution (as high as a few microns) for recording the dose profile of microbeams which is readout using a confocal fluorescence microscopy technique. These plates are restorable as well and the response is reproducible. The effects of previous X-ray exposure including samarium valency conversion as well as induced absorbance may be erased by annealing at temperatures exceeding the glass transition temperature Tg while annealing at TA < Tg enhances the response. This enhancement is explained by a thermally stimulated relaxation of host glass ionic matrix surrounding X-ray induced Sm2+ ions. Optical erasure is another practical means to erase the recorded data. Nearly complete Sm2+ to Sm3+ reconversion (erasure) is achieved by intense optical illumination at 405 nm. While, existing X-ray induced bands would be only partially erased. Electron spin resonance (ESR) and optical absorbance spectroscopy are used to investigate the nature of X-ray induced defects and their correlation with Sm valency conversion. A model based on competition between defect center formation and the Sm3+ ⇆ Sm2+ conversion successfully explains the different processes occurring in the glass matrix under X-ray irradiation

On-board multispectral classification study. Volume 2: Supplementary tasks

The operational tasks of the onboard multispectral classification study were defined. These tasks include: sensing characteristics for future space applications; information adaptive systems architectural approaches; data set selection criteria; and onboard functional requirements for interfacing with global positioning satellites

Digital imaging technology assessment: Digital document storage project

An ongoing technical assessment and requirements definition project is examining the potential role of digital imaging technology at NASA's STI facility. The focus is on the basic components of imaging technology in today's marketplace as well as the components anticipated in the near future. Presented is a requirement specification for a prototype project, an initial examination of current image processing at the STI facility, and an initial summary of image processing projects at other sites. Operational imaging systems incorporate scanners, optical storage, high resolution monitors, processing nodes, magnetic storage, jukeboxes, specialized boards, optical character recognition gear, pixel addressable printers, communications, and complex software processes

Composable and Robust Outsourced Storage

The security of data outsourcing mechanisms has become a crucial aspect of today\u27s IT infrastructures and are the cryptographic foundations of real-world applications. The very fundamental goals are ensuring storage integrity and auditability, confidentiality, and access pattern hiding, as well as combinations of all of them. Despite sharing a common setting, security analyses of these tasks are often performed in a stand-alone fashion expressed in different models, which makes it hard to assess the overall security of a protocol or application involving several security schemes at once. In this work, we fill this gap and propose a composable framework suitable to capture various aspects of outsourced storage security and its applications. We instantiate the basic client-server setting in this model, where the goal of the honest client is to retain security in the presence of a malicious server. Three specific contributions of this paper are: 1.) We present a novel definition for secure and robust outsourcing schemes and underline why this is needed in practice. Our definition is stronger than previous definitions for oblivious RAM or software protection in that it assures strong security guarantees against active attacks. Schemes meeting the definition not only assure that an attacker cannot learn the access pattern, but guarantee resilience to errors and the prevention of targeted attacks to specific locations. Unfortunately, several existing schemes cannot achieve this high level of security. For completeness, we provide a protocol based on Path ORAM that showcases that stronger security is actually achievable. 2.) We present a novel definition for auditable storage, capturing the guarantee that a successful audit implies that the current server state allows the client to retrieve his data. We develop an audit mechanism, based on secure and robust outsourcing schemes, that is similar to the construction by Cash et al. (Eurocrpyt 2013), but is universally composable and fault-tolerant. 3.) We revisit the security claim of a widely-used challenge-response audit mechanism, in which the server has to compute a hash $H(F||c)$ on the file $F$ concatenated with a uniformly random challenge $c$ chosen by the client. Being concerned with composable security, we prove that this audit mechanism is not secure, even in the random oracle model, without additional assumptions. The composable security of this basic audit scheme was implicitly assumed in Ristenpart et al. (Eurocrypt 2011). To complete the picture, we state the additional assumptions for this audit mechanism to be provably secure and investigate the (in)applicability of hash-function constructions in this setting

Research studies on advanced optical module/head designs for optical devices

A summary is presented of research in optical data storage materials and of research at the center. The first section contains summary reports under the general headings of: (1) Magnetooptic media: modeling, design, fabrication, characterization, and testing; (2) Optical heads: holographic optical elements; and (3) Optical heads: integrated optics. The second section consist of a proposal entitled, Signal Processing Techniques for Optical Data Storage. And section three presents various publications prepared by the center

In situ Manipulation of Magnetization via Direct Mechanical Interaction in Magnetostrictive Thin Films

The pursuit of a universal memory- possessing fast write/read times, nonvolatile and unlimited data endurance, low operating power, low manufacture costs, high bit density, as well as being easily integrable with on-trend complementary metal-oxide semiconductor (CMOS) devices- has reenergized research in the field of multiferroic and magnetoelectric materials. Such materials simultaneously exhibit ferroelectricity and ferromagnetism, and allow for the coupling of the two order parameters, known as magnetoelectric coupling. This coupling is enhanced in magnetostrictive/piezoelectric bilayer systems where applied electrical bias can modify magnetic order via strain-mediation, a mechanism that can reduce the power demands in emerging magnetic random access memory (MRAM) technologies. We have previously investigated this relationship in an Fe0.7Ga0.3/BaTiO3 bilayer structure using magnetic contrast imaging techniques with in situ applied electric fields. The goal of this thesis was to explore methods to better control magnetoelectric effects in order to enhance local magnetic response to external stimuli. Specifically, we investigated magnetoelastic response of freestanding, magnetostrictive Fe0.7Ga0.3 thin films via direct mechanical interaction with an external probe, as the well known strain-mediated mechanism in magnetoelectric devices depends on the lesser known magnetoelastic nature of strain transfer between the distinct material phases. Magnetoelastic effects are directly associated with both external magnetic field and stress via Lorentz-force transmission electron microscopy (LTEM) contrast techniques, and the hysteresis of magnetic order was charted with respect to both stimuli. For relevant application to MRAM devices, we have initiated studying these effects in patterned media as well, where individual, nanoscale magnetic geometries represent bistable bits for memory. We demonstrate static pure stress effects on the magnetoelastic response in continuous thin films, as well as real-time mechanical "writing" of stable domain states. The external probe is directed into the film, inducing a non-uniform, radially symmetric local strain. Micromagnetic simulation reveals that the strength of observed magnetoelastic effects is offset by small, undulating variations in magnetization characteristic of polycrystalline thin films, known as magnetization ripple. Imposing a threshold function on the effective anisotropy of the film describes the spontaneous onset of these effects and the differences in magnetic order for films with hysteresis solely due to stress, or with both field and stress. Thus, a method to achieve bistable logic for MRAM applications using direct uniform stress, in lieu of external fields, is proposed

A cognitive model of fiction writing.

Models of the writing process are used to design software tools for writers who work with computers. This thesis is concerned with the construction of a model of fiction writing. The first stage in this construction is to review existing models of writing. Models of writing used in software design and writing research include behavioural, cognitive and linguistic varieties. The arguments of this thesis are, firstly, that current models do not provide an adequate basis for designing software tools for fiction writers. Secondly, research into writing is often based on questionable assumptions concerning language and linguistics, the interpretation of empirical research, and the development of cognitive models. It is argued that Saussure's linguistics provides an alternative basis for developing a model of fiction writing, and that Barthes' method of textual analysis provides insight into the ways in which readers and writers create meanings. The result of reviewing current models of writing is a basic model of writing, consisting of a cycle of three activities - thinking, writing, and reading. The next stage is to develop this basic model into a model of fiction writing by using narratology, textual analysis, and cognitive psychology to identify the kinds of thinking processes that create fictional texts. Remembering and imagining events and scenes are identified as basic processes in fiction writing; in cognitive terms, events are verbal representations, while scenes are visual representations. Syntax is identified as another distinct object of thought, to which the processes of remembering and imagining also apply. Genette's notion of focus in his analysis of text types is used to describe the role of characters in the writer's imagination: focusing the imagination is a process in which a writer imagines she is someone else, and it is shown how this process applies to events, scenes, and syntax. It is argued that a writer's story memory, influences his remembering and imagining; Todorov's work on symbolism is used to argue that interpretation plays the role in fiction writing of binding together these two processes. The role of naming in reading and its relation to problem solving is compared with its role in writing, and names or signifiers are added to the objects of thought in fiction writing. It is argued that problem solving in fiction writing is sometimes concerned with creating problems or mysteries for the reader, and it is shown how this process applies to events, scenes, signifiers and syntax. All these findings are presented in the form of a cognitive model of fiction writing. The question of testing is discussed, and the use of the model in designing software tools is illustrated by the description of a hypertextual aid for fiction writers