Charles Allen

QR codes are increasingly being used as a mechanism to transmit one time passwords (OTPs) between devices for the purpose of authentication due to their convenience, low cost, and the ubiquity of consumer mobile devices. Existing practice typically utilizes a single QR code which is relatively easy to capture and relay to an offsite attacker or collaborator. We propose a mechanism using a stream of rapidly changing QR codes that maintains the convenience, ubiquity, and low cost of the standard approach, while aiming to eliminate the viability of relay attacks. We test this setup using a university class attendance scenario and successfully distinguish between valid physically present users and invalid offsite attackers.

A central promise of Model-Based Systems Engineering (MBSE) is to provide all members of a development team with the right tools to manage all information about their product throughout its life-cycle. The key to deliver this promise is a pragmatic methodology without introducing new overheads, steep learning curves or the need to buy expensive software. The Model-Driven Development Approach (MDDP) addresses these issues by combining best-practices from MBSE and Lean Information Management. It provides a structure for all salient Systems Engineering (SE) data in a central model that stretches across all architectural layers and allows the automatic generation of various specialists' perspectives in different formats, such as diagrams, graphs, tables, matrices, reports etc.

Variant exploration is often construed as synonymous with a significant increase in work and a decrease in clarity. Model-Based Systems Engineering (MBSE) has been heralded as a potential solution to streamline the process by supporting exploration of numerous parallel variants within a common multidimensional model. Successful decoupling of variants from their surroundings supports the parallel development of interfacing systems without delay or impediment, thereby permitting the deferment of a final decision on the preferred technology choice. Still, a number of challenges remain. Some have been addressed by previous research, though, not focusing on the effect of variant technology choices in the logical tier, nor on embedding variant management as a native part of the core MBSE model. This paper addresses those challenges via application of Liskov's Substitution Principle (LSP). It defines an MBSE based approach that explicitly documents variance points, identifying their source and scope, and integrates their management into the standard Systems Engineering (SE) workflow. Emphasis is given on providing a pragmatic approach that promotes consistency, visibility, and simplicity. The result is a model that embeds the required information artifacts without adding significant complexity. The proposed strategy does not prescribe excessive variant-specific activities, with the majority of the effort being already part of standard Requirement, Interface, and Logical SE processes. It is tolerant to an iterative approach, and proactively supports concurrent engineering through decoupling.

A central promise of Model-Based Systems Engineering (MBSE) is to decrease the volume of information produced during the system design lifecycle through improved structure and smarter reuse across the numerous perspectives and architectural levels. The study of variants is a core challenge within MBSE due to associated exponential information growth, and the complexity created by this extra dimensionality. Variant management has been discussed extensively for the physical layer, but lacks research focusing on functional and logical layers, particularly relevant to concept phase engineering. In System of Systems (SoS) problems, the physical choices are typically constrained by the fact that the interacting systems already exist. This paper therefore studies the implications of variant modelling for the behaviour of the SoS. It explores the possibility of developing a functional architecture that can be extended to accommodate changes due to decisions made in the logical layer. It investigates the formal aspects of including variant modelling into the Systems Modelling Language (SysML) and discusses the potential need for a language extension.