Symmetric encryption is the most commonly employed security solution in wireless sensor networks (WSNs). In this paper, a new approach that employs public-key cryptography during key establishment is proposed. In a WSN, the main issue for public-key cryptography is represented by communication and computational overheads. In order to reduce these requirements, a new authentication system based on authentication tables is proposed. An analytical study shows that the proposed approach provided optimal protection against an adversary that compromised one or more nodes. A comparative analysis shows that, according to the dimension and the density of the network, the proposed approach can represent the best solution. Furthermore, an experimental analysis conducted on a real network shows that the proposed approach can be successfully applied to devices with limited computational power.

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Thresholds of vision under low-light conditions have been studied for determining the human response to light stimuli in different contexts. Blackwell's work on thresholds of vision of the human visual system did not explore some variables whose analysis would help to characterize more deeply the visual system. This paper extends Blackwell's results exploring new dimensions of the human visual system response including chromaticity of the stimuli, mono/binocular vision, and dark adaptation. Tests have been performed on a sample of 45 observers, with a simplified laboratory setup with respect to Blackwell and without specific hardware/software, producing results in terms of visual adaptation, monocular, and binocular vision and aging effects.