This paper presents Unikernel Linux (UKL), a path toward integrating unikernel optimization techniques in Linux, a general purpose operating system. UKL adds a configuration option to Linux allowing for a single, optimized process to link with the kernel directly, and run at supervisor privilege. This UKL process does not require application source code modification, only a re-link with our, slightly modified, Linux kernel and glibc. Unmodified applications show modest performance gains out of the box, and developers can further optimize applications for more significant gains (e.g. 26% throughput improvement for Redis). UKL retains support for co-running multiple user level processes capable of communicating with the UKL process using standard IPC. UKL preserves Linux's battle-tested codebase, community, and ecosystem of tools, applications, and hardware support. UKL runs both on bare-metal and virtual servers and supports multi-core execution. The changes to the Linux kernel are modest (1250 LOC).

This paper presents a system-level method for achieving the rapid deployment and high-density caching of serverless functions in a FaaS environment. For reduced start times, functions are deployed from unikernel snapshots, bypassing expensive initialization steps. To reduce the memory footprint of snapshots we apply page-level sharing across the entire software stack that is required to run a function. We demonstrate the effects of our techniques by replacing Linux on the compute node of a FaaS platform architecture. With our prototype OS, the deployment time of a function drops from 100s of milliseconds to under 10 ms. Platform throughput improves by 51x on workload composed entirely of new functions. We are able to cache over 50,000 function instances in memory as opposed to 3,000 using standard OS techniques. In combination, these improvements give the FaaS platform a new ability to handle large-scale bursts of requests.

The evaluation of SPARQL algebra queries on various kinds of annotated RDF graphs can be seen as a particular case of the evaluation of these queries on RDF graphs annotated with elements of so-called spm-semirings . Spm-semirings extend semirings, used for representing the provenance of positive relational algebra queries on annotated relational data, with a new operator to capture the semantics of the non-monotone SPARQL operators. Furthermore, spm-semiring-based annotations ensure that desired SPARQL query equivalences hold when querying annotated RDF. In this work, in addition to introducing spm-semirings, we study their properties and provide an alternative characterization of these structures in terms of semirings with an embedded boolean algebra (or seba-structure for short). This characterization allows us to construct spm-semirings and identify a universal object in the class of spm-semirings. Finally, we show that this universal object provides a provenance representation of poly-sized overhead and can be used to evaluate SPARQL queries on arbitrary spm-semiring-annotated RDF graphs.

Session hijacking has become a major problem in today's Web services, especially with the availability of free off-the-shelf tools. As major websites like Facebook, You tube and Yahoo still do not use HTTPS for all users by default, new methods are needed to protect the users' sessions if session tokens are transmitted in the clear. In this paper we propose the use of browser fingerprinting for enhancing current state-of-the-art HTTP(S) session management. Monitoring a wide set of features of the user's current browser makes session hijacking detectable at the server and raises the bar for attackers considerably. This paper furthermore identifies HTML5 and CSS features that can be used for browser fingerprinting and to identify or verify a browser without the need to rely on the User Agent string. We implemented our approach in a framework that is highly configurable and can be added to existing Web applications and server-side session management with ease.

In the context of space-time block codes (STBCs), the theory of generalized quaternion and biquaternion algebras (i.e., tensor products of two quaternion algebras) over arbitrary base fields is presented, as well as quadratic form theoretic criteria to check if such algebras are division algebras. For base fields relevant to STBCs, these criteria are exploited, via Springer's theorem, to construct several explicit infinite families of (bi-)quaternion division algebras. These are used to obtain new 2 × 2 and 4 × 4 STBCs.