Securing Interruptible Enclaved Execution on Small Microprocessors

Computer systems often provide hardware support for isolation mechanisms such as privilege levels, virtual memory, or enclaved execution. Over the past years, several successful software-based side-channel attacks have been developed that break, or at least significantly weaken, the isolation that these mechanisms offer. Extending a processor with new architectural or micro-architectural features brings a risk of introducing new software-based side-channel attacks. This article studies the problem of extending a processor with new features without weakening the security of the isolation mechanisms that the processor offers. Our solution is heavily based on techniques from research on programming languages. More specifically, we propose to use the programming language concept of full abstraction as a general formal criterion for the security of a processor extension. We instantiate the proposed criterion to the concrete case of extending a microprocessor that supports enclaved execution with secure interruptibility. This is a very relevant instantiation, as several recent papers have shown that interruptibility of enclaves leads to a variety of software-based side-channel attacks. We propose a design for interruptible enclaves and prove that it satisfies our security criterion. We also implement the design on an open-source enclave-enabled microprocessor and evaluate the cost of our design in terms of performance and hardware size.

Blame and coercion: Together again for the first time

C#, Dart, Pyret, Racket, TypeScript, VB: many recent languages integrate dynamic and static types via gradual typing. We systematically develop four calculi for gradual typing and the relations between them, building on and strengthening previous work. The calculi are as follows: $\lambda{B}$ , based on the blame calculus of Wadler and Findler (2009); $\lambda{C}$ , inspired by the coercion calculus of Henglein (1994); $\lambda{S}$ inspired by the space-efficient calculus of Herman, Tomb, and Flanagan (2006); and $\lambda{T}$ based on the threesome calculus of Siek and Wadler (2010). While $\lambda{B}$ and $\lambda{T}$ are little changed from previous work, $\lambda{C}$ and $\lambda{S}$ are new. Together, $\lambda{B}$ , $\lambda{C}$ , $\lambda{S}$ , and $\lambda{T}$ provide a coherent foundation for design, implementation, and optimization of gradual types. We define translations from $\lambda{B}$ to $\lambda{C}$ , from $\lambda{C}$ to $\lambda{S}$ , and from $\lambda{S}$ to $\lambda{T}$ . Much previous work lacked proofs of correctness or had weak correctness criteria; here we demonstrate the strongest correctness criterion one could hope for, that each of the translations is fully abstract. Each of the calculi reinforces the design of the others: $\lambda{C}$ has a particularly simple definition, and the subtle definition of blame safety for $\lambda{B}$ is justified by the simple definition of blame safety for $\lambda{C}$ . Our calculus $\lambda{S}$ is implementation-ready: the first space-efficient calculus that is both straightforward to implement and easy to understand. We give two applications: first, using full abstraction from $\lambda{C}$ to $\lambda{S}$ to establish an equational theory of coercions; and second, using full abstraction from $\lambda{B}$ to $\lambda{S}$ to easily establish the Fundamental Property of Casts, which required a custom bisimulation and six lemmas in earlier work.

Abs-Sum-Kan: An Abstractive Text Summarization Technique for an Indian Regional Language by Induction of Tagging Rules

This paper presents a full abstraction for Indian languages, specifically Kannada, in the context of guided summarization. The proposed process generates the abstractive summary by focusing on a unified presentation model with aspect based Information Extraction (IE) rules and scheme based Templates. TF/IDF rules are used for classification into categories. Lexical analysis (like Parts Of Speech tagging and Named Entity Recognition) reduces prolixity, which leads to robust IE rules. Usage of Templates for sentence generation makes the summaries succinct and information intensive. The IE rules are designed to accommodate the complexities of the considered languages. Later, the system aims to produce a guided summary of domain specific documents. An abstraction scheme is a collection of aspects and associated IE rules. Each abstraction scheme is designed based on a theme or subcategory. An extensive statistical and qualitative evaluation of the summaries generated by the system has been conducted and the results are found to be very promising.

Abs-Sum-Kan: An Abstractive Text Summarization Technique for an Indian Regional Language by Induction of Tagging Rules

This paper presents a full abstraction for Indian languages, specifically Kannada, in the context of guided summarization. The proposed process generates the abstractive sum-mary by focusing on a unified presentation model with aspect based Information Extrac-tion (IE) rules and scheme based Templates. TF/IDF rules are used for classification into categories. Lexical analysis (like Parts Of Speech tagging and Named Entity Recognition) reduces prolixity, which leads to robust IE rules. Usage of Templates for sentence genera-tion makes the summaries succinct and information intensive. The IE rules are designed to accommodate the complexities of the considered languages. Later, the system aims to produce a guided summary of domain specific documents. An abstraction scheme is a collection of aspects and associated IE rules. Each abstraction scheme is designed based on a theme or subcategory. An extensive statistical and qualitative evaluation of the summaries generated by the system has been conducted and the results are found to be very promising.

Parameterizing higher-order processes on names and processes

Parameterization extends higher-order processes with the capability of abstraction and application (like those in lambda-calculus). As is well-known, this extension is strict, meaning that higher-order processes equipped with parameterization are strictly more expressive than those without parameterization. This paper studies strictly higher-order processes (i.e., no name-passing) with two kinds of parameterization: one on names and the other on processes themselves. We present two main results. One is that in presence of parameterization, higher-order processes can interpret first-order (name-passing) processes in a quite elegant fashion, in contrast to the fact that higher-order processes without parameterization cannot encode first-order processes at all. We present two such encodings and analyze their properties in depth, particularly full abstraction. In the other result, we provide a simpler characterization of the standard context bisimilarity for higher-order processes with parameterization, in terms of the normal bisimilarity that stems from the well-known normal characterization for higher-order calculus. As a spinoff, we show that the bisimulation up-to context technique is sound in the higher-order setting with parameterization.

Nagdi, Omar el- (1931--)

Omar el-Nagdi began his art education at the Faculty of Fine Arts in Cairo and graduated with a bachelor’s degree in 1953. He received a second bachelor’s degree in 1957 from the Faculty of Applied Arts in Cairo. In addition to his studies in Egypt, El-Nagdi studied abroad in Russia, Italy and Holland. Beginning in 1957, El-Nagdi served as an instructor at the Faculty of Applied Arts in Cairo. Omar el-Nagdi’s early works were primarily figural paintings inspired by Egyptian folk traditions. In the 1960s, he shifted to full abstraction and the calligraphic Arabic letters became a prominent theme in his work. El-Nagdi also created a running series of sculptural works that translated the angular figures from his early paintings into three-dimensional forms.