Papers by Aleksandar Ignjatovic
Proceedings of the 54th Annual Design Automation Conference 2017, 2017
Hardware Trojans are a major concern due to the damage caused by their stealth. One popular utili... more Hardware Trojans are a major concern due to the damage caused by their stealth. One popular utilization of Multiprocessor System on Chips (MPSoCs) is the Pipelined MPSoC (PMPSoC) architectures. They are used in applications from video surveillance to consumer electronics. We present a method that detects the presence of Trojans in third party IP cores of PMPSoCs, by continuous monitoring and testing, and recovers by switching the infected core with another core. We implemented the system on a commercial cycle accurate multiprocessor simulation environment. Our system incurs about 2× area and leakage power, and 1.5× dynamic power overheads, without any adverse impact on throughput compared to the state of the art that uses Triple Modular Redundancy (TMR) and therefore incurs at least 3× overhead.
IACR Transactions on Cryptographic Hardware and Embedded Systems
Field-programmable gate arrays (FPGAs) deployed on commercial cloud services are increasingly gai... more Field-programmable gate arrays (FPGAs) deployed on commercial cloud services are increasingly gaining popularity due to the cost and compute benefits offered by them. Recent studies have discovered security threats than can be launched remotely on FPGAs that share the logic fabric between trusted and untrusted parties, posing a danger to designs deployed on cloud FPGAs. With remote power analysis (RPA) attacks, an attacker aims to deduce secret information present on a remote FPGA by deploying an on-chip sensor on the FPGA logic fabric. Information captured with the on-chip sensor is transferred off the chip for analysis and existing on-chip sensors demand a significant amount of bandwidth for this task as a result of their wider output bit width. However, attackers are often left with the only option of using a covert communication channel and the bandwidth of such channels is generally limited. This paper proposes a novel area-efficient on-chip power sensor named PPWM that integra...
Hydrological Processes, 2021
Two-dimensional hydrodynamic models numerically solve full Shallow Water Equations (SWEs). Despit... more Two-dimensional hydrodynamic models numerically solve full Shallow Water Equations (SWEs). Despite their high accuracy, these models have long simulation run times and therefore are of limited use for exploratory or real-time flood predictions. We investigated the possibility of improving flood modelling speed using Machine Learning (ML). We propose a new method that replaces the computationally expensive parts of the hydrodynamic models with simple and efficient data-driven approximations. Our hypothesis is that by integrating ML with physics-based numerical methods, we can achieve improved generalization performance: that is, the trained model for one case study can be used in other studies without the need for new training. We tested two ML approaches: for the first, we integrated curve fitting, and, for the second, artificial neural networks (ANN) with a finite volume scheme to solve the local inertial approximation of the SWEs. The data-driven models approximated the Momentum Equation, which explicitly solved the time derivative of flow rates. Water depths were then updated by applying a water balance equation. We also tested two different training datasets: the simulated dataset, generated from the results of hydrodynamic model, and the random dataset, generated by directly solving the momentum equation on randomly sampled input data. Various combinations of input features, for example, water slope and depth, were explored. The proposed models were trained in a small hypothetical case and tested in a different hypothetical and in two real case studies. Results showed that the curve-fitting method can be implemented successfully, given sufficient training and input data. The ANN model trained with a random dataset was substantially more accurate than that of the model trained with the simulated dataset. However, it was not successful in the real case studies. The curve-fitting method resulted in better generalization performance and increased the simulation speed of the local inertial model by 23%. Future research should test the performance of ML in terms of an increase in stable time step size and approximation of the full SWEs.</p
2021 IEEE International Symposium on Circuits and Systems (ISCAS), 2021
A method for acquisition of high bandwidth signals is presented as a typical example of a signal ... more A method for acquisition of high bandwidth signals is presented as a typical example of a signal processing application of chromatic derivatives and approximations. Chromatic derivatives are numerically robust differential operators based on orthogonal polynomials. Theoretical formulations required for synthesising an analog chromatic derivative filterbank based on all-pass filters is presented. Such an analog filterbank with N +1 filters can be used for digital acquisition of high bandwidth signals by simultaneously sampling the outputs of the filterbank at a rate 2/(N + 1) of the Nyquist rate, resulting in samples of the signal and higher order chromatic derivatives up to order N, which in turn are used to reconstruct the original signal back. The value of the signal at any instant is obtained from only two nearest samples of the chromatic derivatives filterbank.
BMC Bioinformatics, 2019
Background: Pairwise alignment of short DNA sequences with affine-gap scoring is a common process... more Background: Pairwise alignment of short DNA sequences with affine-gap scoring is a common processing step performed in a range of bioinformatics analyses. Dynamic programming (i.e. Smith-Waterman algorithm) is widely used for this purpose. Despite using data level parallelisation, pairwise alignment consumes much time. There are faster alignment algorithms but they suffer from the lack of accuracy. Results: In this paper, we present MEM-Align, a fast semi-global alignment algorithm for short DNA sequences that allows for affine-gap scoring and exploit sequence similarity. In contrast to traditional alignment method (such as Smith-Waterman) where individual symbols are aligned, MEM-Align extracts Maximal Exact Matches (MEMs) using a bit-level parallel method and then looks for a subset of MEMs that forms the alignment using a novel dynamic programming method. MEM-Align tries to mimic alignment produced by Smith-Waterman. As a result, for 99.9% of input sequence pair, the computed alignment score is identical to the alignment score computed by Smith-Waterman. Yet MEM-Align is up to 14.5 times faster than the Smith-Waterman algorithm. Fast run-time is achieved by: (a) using a bit-level parallel method to extract MEMs; (b) processing MEMs rather than individual symbols; and, (c) applying heuristics. Conclusions: MEM-Align is a potential candidate to replace other pairwise alignment algorithms used in processes such as DNA read-mapping and Variant-Calling.
2015 International Conference on Compilers, Architecture and Synthesis for Embedded Systems (CASES), 2015
Power based side-channel attacks attempt to obtain the secret key from implementations of cryptog... more Power based side-channel attacks attempt to obtain the secret key from implementations of cryptographic algorithms, such as Advanced Encryption Standard (AES), by analyzing the power traces during execution. Such attacks employ statistical methods to find correlations of power traces with parts of the secret key. In order to be effective, a countermeasure must remove or conceal such a signature. Previous countermeasures have either removed dynamic power signatures or leakage power signatures, but have not demonstrated effectiveness against both. In this paper, for the first time, we propose a balance and rotate technique for block cipher based algorithms and demonstrate it on an AES circuitry to remove the signature of the secret key from both the static and dynamic components of the power traces and further demonstrate that the countermeasure can withstand the path imbalances and process variation effects. Our solution, relies on algorithmically balancing Hamming distances and Hamming weights (where the bit transitions on the registers and gates are balanced, and the total number of 1s and 0s are balanced) by the use of four identical circuits with differing inputs and modified SubByte tables. By randomly rotating the four encryptions, the system is protected against variations, path imbalances and aging effects. When resistance against power analysis attacks is not of high priority, the proposed countermeasure allows components to be switched off to save power, or to run four executions in parallel for high performance. The proposed countermeasure is implemented for AES and tested against CPA and MIA attacks (for up to a million traces) and none of the secret keys were found even after one million power traces (unprotected AES circuit revealed the secret key within 5,000 power traces). This is the smallest known circuit which is capable of withstanding power based side-channel attacks when variations, path imbalances and aging effects are considered.
Lecture Notes in Computer Science, 2014
We consider the problem of data collection from a continental-scale network of mobile sensors, sp... more We consider the problem of data collection from a continental-scale network of mobile sensors, specifically applied to wildlife tracking. Our application constraints favor a highly asymmetric solution, with heavily duty-cycled sensor nodes communicating with a network of powered base stations. Individual nodes move freely in the environment, resulting in low-quality radio links and hot-spot arrival patterns with the available data exceeding the radio link capacity. We propose a novel scheduling algorithm, κ-Fair Scheduling Optimization Model (κ-FSOM), that maximizes the amount of collected data under the constraints of radio link quality and energy, while ensuring a fair access to the radio channel. We show the problem is NP-complete and propose a heuristic to approximate the optimal scheduling solution in polynomial time. We use empirical link quality data to evaluate the κ-FSOM heuristic in a realistic setting and compare its performance to other heuristics. We show that κ-FSOM heuristic achieves high data reception rates, under different fairness and node lifetime constraints.
Chromatic derivatives and series expansions of bandlimited functions have recently been introduce... more Chromatic derivatives and series expansions of bandlimited functions have recently been introduced as an alternative representation to Taylor series and they have been shown to be more useful in practical signal processing applications than Taylor series. The n-th chromatic derivative of an analytic function is a linear combination of its kth ordinary derivatives with 0≤ k≤ n, where the coefficients of the linear combination are based on a suitable system of orthogonal polynomials. The goal of this article is to extend chromatic ...
IEEE Transactions on Signal Processing, 2018
Статья исследует проблему политической эвфемии на материале авторитетных американских и турецких ... more Статья исследует проблему политической эвфемии на материале авторитетных американских и турецких печатных изданий начала ХХI века. Целью статьи является изучение подходов к определению понятия "эвфемизм" в исследованиях российских и западных лингвистов, а также анализ классификаций и функциональных особенностей политических эвфемизмов. В статье представлены результаты исследования, свидетельствующие о достаточно широком использовании политических эвфемизмов в языке современных американских печатных изданий начала ХХI века в отличие от аналогичных турецкоязычных изданий. Адрес статьи: www.gramota.net/materials/2/2016/7-3/49.html
IEEE Transactions on Information Forensics and Security, 2015
Detection of high risk hosts and flows continues to be a significant problem in security monitori... more Detection of high risk hosts and flows continues to be a significant problem in security monitoring of high throughput networks. A comprehensive risk assessment method should take into account the risk propagation among risky hosts and flows. In this paper this is achieved by introducing two novel concepts. The first is an interdependency relationship among the risk scores of a network flow and its source and destination hosts. In one hand, the risk score of a host depends on risky flows such a host initiates and is targeted by. On the other hand, the risk score of a flow depends on the risk scores of its source and destination hosts. The second concept, which we call flow provenance, represents risk propagation among network flows which takes into account the likelihood that a particular flow is caused by other flows. Based on these two concepts, we develop an iterative algorithm for computing the risk level of hosts and network flows. We give a rigorous proof that our algorithm rapidly converges to unique risk estimates, and provide its extensive empirical evaluation using two real-world datasets. Our evaluation demonstrates that our method is effective in detecting high risk hosts and flows and is sufficiently efficient to be deployed in high throughput networks.
Chromatic derivatives and series expansions of bandlimited functions have recently been introduce... more Chromatic derivatives and series expansions of bandlimited functions have recently been introduced as an alternative representation to Taylor series and they have been shown to be more useful in practical signal processing applications than Taylor series. Although chromatic series were originally introduced for bandlimited functions, they have now been extended to a larger class of functions. The n-th chromatic derivative of an analytic function is a linear combination of the kth ordinary derivatives with 0 ≤ k ≤ n, where the coefficients of the linear combination are based on a suitable system of orthogonal polynomials. The goal of this article is to extend chromatic derivatives and series to higher dimensions. This is of interest not only because the associated multivariate orthogonal polynomials have much reacher structure than in the univariate case, but also because we believe that multidimensional case will find natural applications to fields such as image processing and analy...
IEEE Transactions on Network and Service Management
In our work on frequency estimation based on local signal behavior [15] for testing purposes we n... more In our work on frequency estimation based on local signal behavior [15] for testing purposes we needed a signal φ(t) which over some disjoint intervals of (continuous) time In is equal to a corresponding linear combination fn(t) of up to N sine waves, possibly damped and phase shifted, of (normalized) frequencies smaller than π. The signal should also satisfy the following constraints: φ(t) should contain a minimal amount of out-of-band energy, i.e., the energy of its Fourier transform φ(ω) outside interval [-p φ(t) should fit within an as narrow envelope as possible; φ(t) should also have a finite support in the time domain, which is as short as possible. Clearly, these are mutually conflicting requirements and we want to look for a compromise solution which is nevertheless good in all of these respects. A computationally efficient method for producing such a signal can be useful for designing novel digital modulation schemas which satisfy stringent conditions on out of band leakag...
Benchmarking practices in information retrieval rely on measuring the per-topic performances of s... more Benchmarking practices in information retrieval rely on measuring the per-topic performances of systems and aggregating these across the topics in a given test set. For an evaluation experiment, the per-topic scores represent the values in the matrix of the participating systems and the set of topics. In the absence of explicit external reference points indicating the true performance of systems, such a matrix represents a relative view over a sample of the universe of possible system-topic pairs, where a cyclical dependency exists between the systems and the topics. In this paper we develop a unified model for system evaluation by systematically modeling the relationship between topics and systems and by generalizing the way overall system performance is obtained from the individual topic scores with the use of a generalized means function with adaptive weights. We experiment with multiple definitions of the means on TREC evaluation runs and compare our rankings with the standard T...
We present the basic properties of the chromatic derivatives and the chromatic expansions as well... more We present the basic properties of the chromatic derivatives and the chromatic expansions as well as a motivation for introducing these notions. The chromatic derivatives are special, numerically robust linear differential operators; the chromatic expansions are the associated local expansions, which possess the best features of both the Taylor and the Nyquist expansions. This makes them potentially useful in fields involving sampled data, such as signal and image processing.
Malaysian Journal of Computer Science
With the advancement in technology, the size of electronic components and printed circuit boards ... more With the advancement in technology, the size of electronic components and printed circuit boards (PCB) is becoming small while the pin count of each component is increasing. This has necessitated the use of ball grid array (BGA) type of components where pins are attached under the body of component as a grid. The problem of routing pins from under the body of component to the boundary of the component is known as escape routing. It is often desirable to perform ordered simultaneous escape routing (SER) to facilitate area routing and produce elegant PCB design. The task of SER is non-trivial, given the small size of components and hundreds of pins arranged in random order in each component that needs ordered connectivity. In this paper, first we propose flow models for different inter pin capacities. We then propose linear network flow optimization model that simultaneously solves the net ordering and net escape problem. The model routes maximum possible nets between two components of the PCB, by considering the design rules. Comparative analysis shows that the proposed optimization model performs better than the existing routing algorithms in terms of number of nets routed.
Question answering (Q&A) community sites, such as the MSN Qn A a d Yahoo! Answers, facilitate que... more Question answering (Q&A) community sites, such as the MSN Qn A a d Yahoo! Answers, facilitate question answering by a community of us ers. However, the quality of the answers provided by users varies. To determin e the best answer, vote counts, sometimes with extra weight put on the askers, are co mmonly used. This makes the result vulnerable to tainted vote effect as opinio ns from “bad” voters weight the same as those from the “good” ones. We propose a new method to determine the best answer by the sum of voters’ reliability s cores, which are calculated based on voters’ behaviors. The more a voter can choose the best answer, the more reliable he is and the more weight his opinion should car ry. This is a circular definition similar to the reputation score evaluation in [2] . Our method does not require the identification of anomalous voting behavior to red uce the reliability score. Instead, we employ the Brouwer Fixed Point Theorem [1] to sho w the existence of the assignment fo...
Consider a situation in which a group of assessors mark a collection of submissions; each assesso... more Consider a situation in which a group of assessors mark a collection of submissions; each assessor marks more than one submission and each submission is marked by more than one assessor. Typical scenarios include reviewing conference submissions and peer marking in a class. The problem is how to optimally assign a final mark to each submission. The mark assignment must be robust in the following sense. A small group of assessors might collude and give marks which significantly deviate from the marks given by other assessors. Another small group of assessors might give arbitrary marks, uncorrelated with the others’ assessments. Some assessors might be excessively generous while some might be extremely stringent. In each of these cases, the impact of the marks by assessors from such groups has to be appropriately discounted. Based on the work in [2], we propose a method which produces marks meeting the above requirements. The final mark assigned to each submission is a weighted averag...
Federated learning enables a global machine learning model to be trained collaboratively by distr... more Federated learning enables a global machine learning model to be trained collaboratively by distributed, mutually non-trusting learning agents who desire to maintain the privacy of their training data and their hardware. A global model is distributed to clients, who perform training, and submit their newly-trained model to be aggregated into a superior model. However, federated learning systems are vulnerable to interference from malicious learning agents who may desire to prevent training or induce targeted misclassification in the resulting global model. A class of Byzantine-tolerant aggregation algorithms has emerged, offering varying degrees of robustness against these attacks, often with the caveat that the number of attackers is bounded by some quantity known prior to training. This paper presents Simeon: a novel approach to aggregation that applies a reputation-based iterative filtering technique to achieve robustness even in the presence of attackers who can exhibit arbitrar...
I would be very grateful to hear solutions to any of the following questions related to orthogona... more I would be very grateful to hear solutions to any of the following questions related to orthogonal polynomials (or ideas how to tackle these problems or even if they “feel” likely to be true or not). The questions have their origin in digital signal processing, see [1] (found at my website). Thanks in advance, Aleks Ignjatovic, School of Computer Science and Engineering, UNSW, Sydney, NSW 2052, Australia; e-mail : ignjat@cse.unsw.edu.au
Uploads
Papers by Aleksandar Ignjatovic