Καρύμπαλη Ειρήνη

Περίληψη:
Non-Intrusive Load Monitoring (NILM) aims to determine individual-appliance energy consumption with minimum cost, by decomposing aggregated electricity measurements. Although important for achieving energy conservation and cost minimization, NILM requires high-frequency sampling rates to provide accurate results. This requirement significantly increases the need for storage and computational resources in the electric utility’s fog/ cloud infrastructure, and for bandwidth on the customer’s side. To resolve these issues, on-site disaggregation, i.e., on the monitoring device, can be employed. However, to keep device-cost low, lightweight NILM algorithms are needed. To this end, a lightweight event-detection algorithm designed to ease on-site implementation, on either software or hardware, is proposed. Event detection is the first, critical half of the well-established event-based NILM approach; it identifies appliance state changes (events). Although a few lightweight event-detection techniques, utilizing high-frequency data, have been presented in the literature, their performance is relatively low in complex-load cases. The proposed algorithm utilizes simple-to-compute features and employs multiple simple criteria to declare an event as detected, and slope-coefficient inspection to identify steady states. Moreover, it can detect events with very small time difference between them. Comparisons show that its performance is superior even against more complex event-detection approaches, while its low computational cost is also verified.

Περίληψη:
While logic locking is a promising defense to protect hardware designs, many attacks have been shown to undermine its security by retrieving the secret key. All the powerful attacks rely on a working chip, i.e., an oracle, and in particular, heavily use the test access. The proposed technique DisORC turns the oracle into a dishonest one whenever a potential attack is detected. DisORC works on the premise that structural testing of chips need not be performed with the correct functionality. We implement this capability by adding circuitry around a logic-locked design that reconfigures its functionality upon detecting access to scan chains. Any attempt to access scan chains disconnects the secret key from the circuit, and clears all of its traces, isolating and securing it. We also pair this defense with a truly random logic locking (TRLL) scheme that makes random decisions in inserting key gates and retaining signal polarities without relying on any logic synthesis technique to perform bubble pushing. Any netlist analysis-based attack, known or anticipated, will then learn nothing useful to infer the key values. The combined defense DisORC + TRLL thwarts oracle-based and netlist analysis-based attacks while delivering sufficient corruption levels at the outputs. We also show that the proposed defense is cost effective and can be integrated into the design flow easily. The proposed logic locking defense provides protection against untrusted foundry, testing facility, end users, and any combination of them colluding together.

Περίληψη:
The prevalence of wireless networks has made the long-term need for communications security more imperative. In various wireless applications, images and/or video constitute critical data for transmission. For their copyright protection and authentication, watermarking can be used. In many cases, the cost of wireless nodes must be kept low, which means that their processing and/or power capabilities are very limited. In such cases, low-cost hardware implementations of digital image/video watermarking techniques are necessary. However, to end up with such implementations, proper selection of watermarking techniques is not enough. For this reason, in this paper, we introduce computation optimizations of the implemented algorithm to keep the integer part of arithmetic operations at optimal size, and, hence, arithmetic units as small as possible. In addition, further analysis is performed to reduce quantization error. Three different hardware-architecture variants, two for image watermarking and one for video (pipelined), are proposed, which reutilize the already small arithmetic units in different computation steps, to further reduce implementation cost. The proposed designs compare favorably to already existing implementations in terms of area, power, and performance. Moreover, the watermarked images'/frames' errors, compared to their floating point counterparts, are very small, while robustness to various attacks is high.

Περίληψη:
In this paper a new technique for performing image registration with subpixel accuracy is presented. The proposed technique, which is based on the maximization of the correlation coefficient function, does not require the reconstruction of the intensity values and provides a closed-form solution to the subpixel translation estimation problem. Moreover, an efficient iterative scheme is proposed, which reduces considerably the overall computational cost of the image registration problem. This scheme properly combined with the proposed similarity measure results in a fast spatial domain technique for subpixel image registration.

Περίληψη:
The aim of this paper is to improve the performance of spatial domain watermarking. To this end, a new perceptual mask and a new detection scheme are proposed. The proposed spatial perceptual mask is based on the cover image prediction error sequence and matches very well with the properties of the human visual system. It exhibits superior performance compared to existing spatial masking schemes. Moreover, it allows for a significantly increased strength of the watermark while, at the same time, the watermark visibility is decreased. The new blind detection scheme comprises an efficient prewhitening process and a correlation-based detector. The prewhitening process is based on the least-squares prediction error filter and substantially improves the detector’s performance. The correlation-based detector that was selected is shown to be the most suitable for the problem at hand. The improved performance of the proposed detection scheme has been justified theoretically for the case of linear filtering plus noise attack and through extensive simulations. The theoretical analysis is independent of the proposed mask and the derived expressions can be used for any watermarking technique based on spatial masking. It is shown though that in most cases the detector performs better if the proposed mask is employed.