Algorithms for switching between block-wise and arithmetic masking

The task of ensuring the required level of security of information systems in the adversary models with additional data obtained through side channels (a striking example of implementing threats in such a model is a differential power analysis) has become increasingly relevant in recent years. An effective protection method against side-channel attacks is masking all intermediate variables used in the algorithm with random values. At the same time, many algorithms use masking of different kinds, for example, Boolean, byte-wise, and arithmetic; therefore, a problem of switching between masking of different kinds arises. Switching between Boolean and arithmetic masking is well studied, while no solutions have been proposed for switching between masking of other kinds. This article recalls the requirements for switching algorithms and presents algorithms for switching between block-wise and arithmetic masking, which includes the case of switching between byte-wise and arithmetic masking

Data Processing and Investigations for the GRACE Follow-On Laser Ranging Interferometer

This thesis presents first in-depth results of the Laser Ranging Interferometer (LRI) onboard the Gravity Recovery And Climate Experiment - Follow On (GRACE-Follow On) mission. The LRI is a novel instrument, which was developed in a U.S.-German collaboration including the Albert-Einstein Institute (AEI) in Hanover. It successfully demonstrated the feasibility of ranging measurements by means of laser interferometry between two distant spacecraft and will push space-borne gravimetry missions to the next sensitivity level. The author of this thesis contributed to this project by programming a comprehensive framework for ground-processing of LRI telemetry and analyzing various kinds of instrument data streams. Therefore, the title of this thesis covers both topics, data processing and investigations within the data. Within this thesis, an introduction to laser interferometry is given and the various payloads of the GRACE-Follow On satellites are presented. Furthermore, the design of the LRI itself is discussed, in order to understand the profound causal relations when getting into the details of investigations. The various kinds of telemetry data and their processing levels are presented, giving an insight about the variety of data sets, that are downlinked from the satellites. The investigations cover various major topics. These reach from different models to assess the absolute laser frequency, which sets the scale to convert the raw phase measurements into corresponding inter-satellite displacements, and comprise a detailed investigation of the carrier to noise ratio, which provides information about the signal quality. Furthermore, the laser’s beam properties in the far-field are investigated by means of the intensity and the phasefront. These investigations even lead to a proposal for a new scan pattern, which has actually been performed. Last but not least, a comprehensive assessment of the LRI spectrum was performed, which reveals correlation between the satellite’s attitude and orbit control system (AOCS), i.e. the star cameras for attitude determination and thruster activations for attitude control, and the ranging signal, measured by the LRI. In summary, this thesis is concerned with several aspects of the LRI characterization and data analysis. Since the overall data quality and sensitivity of the LRI exceeds the needs and expectations for the current gravimetric mission, many of the discussed effects are rather of academic interest, e.g. to deepen the instrument understanding of the LRI team and for the development of future missions in the field of geodesy or the space-based gravitational wave detection (LISA mission)

Efficient Conversion Method from Arithmetic to Boolean Masking in Constrained Devices

A common technique employed for preventing a side channel analysis is boolean masking. However, the application of this scheme is not so straightforward when it comes to block ciphers based on Addition-Rotation-Xor structure. In order to address this issue, since 2000, scholars have investigated schemes for converting Arithmetic to Boolean (AtoB) masking and Boolean to Arithmetic (BtoA) masking schemes. However, these solutions have certain limitations. The time performance of the AtoB scheme is extremely unsatisfactory because of the high complexity of $\mathcal{O}(k)$ where $k$ is the size of addition bit. At the FSE 2015, an improved algorithm with time complexity $\mathcal{O}(\log k)$ based on the Kogge-Stone carry look-ahead adder was suggested. Despite its efficiency, this algorithm cannot consider for constrained environments. Although the original algorithm naturally extends to low-resource devices, there is no advantage in time performance; we call this variant as the generic variant. In this study, we suggest an enhanced variant algorithm to apply to constrained devices. Our solution is based on the principle of the Kogge-Stone carry look-ahead adder, and it uses a divide and conquer approach. In addition, we prove the security of our new algorithm against first-order attack. In implementation results, when $k=64$ and the register bit size of a chip is $8$, $16$ or $32$, we obtain $58$\%, $72$\%, or $68$\% improvement, respectively, over the results obtained using the generic variant. When applying those algorithms to first-order SPECK, we also achieve about $40$\% improvement. Moreover, our proposal extends to higher-order countermeasures as previous study

SoK: SCA-secure ECC in software – mission impossible?

This paper describes an ECC implementation computing the X25519 keyexchange protocol on the Arm Cortex-M4 microcontroller. For providing protections against various side-channel and fault attacks we first review known attacks and countermeasures, then we provide software implementations that come with extensive mitigations, and finally we present a preliminary side-channel evaluation. To our best knowledge, this is the first public software claiming affordable protection against multiple classes of attacks that are motivated by distinct real-world application scenarios. We distinguish between X25519 with ephemeral keys and X25519 with static keys and show that the overhead to our baseline unprotected implementation is about 37% and 243%, respectively. While this might seem to be a high price to pay for security, we also show that even our (most protected) static implementation is at least as efficient as widely-deployed ECC cryptographic libraries, which offer much less protection

The Difficult Impossible: Writing, Perfomance and the Subject

This thesis summarises a period of practice-led research into relationships between imting and performance. It considers ways in which performance (especially performance art) might serve as a critical and methodological lens through which to explore the practice of writing — primarily the author's own. It is located in the recentiy designated field of Performance Writing, whose interdisciplinary approach it adopts. Responding to a perceived condition of impasse (not writing) in the author's relationship to textual production, the thesis charts a process of deploying performance (and subsequentiy video) art as a research methodology, using its emphasis on temporal, spatial, material and corporeal concerns, to focus on writing as material and physical act - aspects of writing that are magnified by the experience of being a miter not imting. The thesis suggests that the experience of impasse was symptomatic of difficulties reconciling the relationship between language and subjectivity, and that this difficulty originates in the author's exposure to certain theological and doctrinal practices. It acknowledges, however, that the emphasis on ritual performativity and embodiment in much Christian liturgy has shaped both his relationship .to the written word, and his performance-based approach to challenging the condition of impasse itself. The thesis is divided into two main parts: the first considers context and methodology; the second tracks the narrative of the research, from the condition of impasse to the production of poetic writing. Sub-divided into three phases {Performing (not) Writing^ Hybrid Practice and Poetry and Performance, the second part deploys differing modes: fragments of autobiographical narrative, specific theoretical discussions, examples of, and commentaries on, practical experiments, and the inclusion of practical work itself. The thesis draws on specific theoretical and philosophical perspectives that are themselves engaged with interplay between questions of writing, subjectivity and interdisciplinarity - most notably those of Jacques Derrida and Helene Cixous.Dartington College of Art

Formal Verification of Arithmetic Masking in Hardware and Software

Masking is a popular secret-sharing technique that is used to protect cryptographic implementations against physical attacks like differential power analysis. So far, most research in this direction has focused on finding efficient Boolean masking schemes for well-known symmetric cryptographic algorithms like AES and Keccak. However, especially with the advent of post-quantum cryptography (PQC), arithmetic masking has received increasing attention from the research community. In practice, many PQC algorithms require a combination of arithmetic and Boolean masking, which makes the search for secure and efficient conversion algorithms between these domains (A2B/B2A) an interesting but very challenging research topic. While there already exist lots of tools that can help with the formal verification of Boolean masked implementations, the same cannot be said about arithmetic masking and accompanying mask conversion algorithms. In this work, we demonstrate the first formal verification approach for (any-order) Boolean and arithmetic masking which can be applied to both hardware and software, while considering side-effects such as glitches and transitions. First, we show how a formal verification approach for Boolean masking can be used in the context of arithmetic masking such that we can verify A2B/B2A conversions for arbitrary masking orders. We investigate various conversion algorithms in hardware and software, and point out several new findings such as glitch-based issues for straightforward implementations of [CGV14]-A2B in hardware, transition-based leakage in Goubin-A2B in software, and more general implementation pitfalls when utilizing common optimization techniques in PQC. We provide the first formal analysis of table-based A2Bs from a probing security perspective and point out that they might not be easy to implement securely on processors that use of memory buffers or caches

Stumbling Blocks Before the Blind

Blind -- France -- History -- To 1500.;Blind -- Great Britain -- History -- To 1500.;Disability studies

Stumbling Blocks Before the Blind

Blind -- France -- History -- To 1500.;Blind -- Great Britain -- History -- To 1500.;Disability studies

Security assemblages: enclaving, private security, and new materialism in suburban Johannesburg

A research report submitted in partial satisfaction of the requirements of the degree Master of Arts in Anthropology March 2016This research report explores how private security is materially assembled in suburban Johannesburg. Based on ethnographic fieldwork within a private security company operating across the northern suburbs of Greater Johannesburg, it examines how the materiality of security is intimately intertwined with shaping the socio-spatial terrain of the city. Using a new materialist “assemblage” theory proposed by Jane Bennett, it contends although the materials of private security are designed to protect and exclude, they often work rather differently on the ground, resulting in strange new ways of seeing, moving, and relating in the city