Aleksandar Ignjatović

• PhD
• Professor (Associate) at UNSW Sydney

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 de...

On-chip sensors, built using reconfigurable logic resources in field programmable gate arrays (FPGAs), have been shown to sense variations in signalpropagation delay, supply voltage and power consumption. These sensors have been successfully used to deploy security attacks called Remote Power Analysis (RPA) Attacks on FPGAs. The sensors proposed th...

This paper presents UCloD, a novel random clock delay-based robust and scalable countermeasure against recently discovered remote power analysis (RPA) attacks. UCloD deploys very small clock delays (in the picosecond range) generated using the tapped delays lines (TDLs) to mitigate RPA attacks. UCloD provides the most robust countermeasures demonst...

Side channel analysis attacks employ the emanated side channel information to deduce the secret keys from cryptographic implementations by analyzing the power traces during execution or scrutinizing faulty outputs. To be effective, a countermeasure must remove or conceal as many as possible side channels. However, many of the countermeasures agains...

Authorization or access control limits the actions a user may perform on a computer system, based on predetermined access control policies, thus preventing access by illegitimate actors. Access control for the Internet of Things (IoT) should be tailored to take inherent IoT network scale and device resource constraints into consideration. However,...

Authorization or access control limits the actions a user may perform on a computer system, based on predetermined access control policies, thus preventing access by illegitimate actors. Access control for the Internet of Things (IoT) should be tailored to take inherent IoT network scale and device resource constraints into consideration. However,...

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 supe...

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 propos...

Multiprocessor System-on-Chip (MPSoC) has become necessary due to the the billions of transistors available to the designer, the need for fast design turnaround times, and the power wall. Thus, present embedded systems are designed with MPSoCs, and one possible way MPSoCs can be realized is through Pipelined MPSoC (PMPSoC) architectures, which are...

With the tremendous growth of Web applications and services, eXtensible Access Control Markup Language (XACML) has been broadly adopted to specify Web access control policies. However, when the policies are large or defined by multiple authorities, it has proved difficult to analyze errors and vulnerabilities in a manual fashion. Recent advances in...

The engineering of high rate electrochemical energy storage devices can benefit from analysis techniques that can accurately attribute charge storage to individual energy storage mechanisms. A new time-domain analysis for potentiostatic intermittent titration technique (PITT) experiments that uses Laplace domain representations of impedance is pres...

Random execution time-based countermeasures against power analysis attacks have reduced resource overheads when compared to balancing power dissipation and masking countermeasures. The previous countermeasures on randomization use either a small number of clock frequencies or delays to randomize the execution. This paper presents a novel random fre...

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 alg...

Recently, there has been great deal of interest in high rate electrochemical energy storage. We are now at a point where the distinction between high rate Li-ion batteries and high energy electrochemical capacitors has begun to blur 1, 2 . There is hence an interest in elucidating the nature of charge storage in these high rate systems, with the ai...

We propose a novel adaptive denoising algorithm which, in presence of high levels of noise, significantly improves super-resolution and noise robustness of standard frequency estimation algorithms such as (root-)MUSIC and ESPRIT. During the course of its operation, the algorithm dynamically estimates the power spectral density (PSD) of noise and ad...

The well known Logan's theorem asserts that, under some assumptions, a one octave bandpass signal is recoverable, modulo a multiplicative constant, from its zero crossings only. However, such recovery is numerically problematic and the theorem is not applicable to general bandlimited signals. In this paper, we demonstrate that the additional timing...

A novel, highly accurate signal reconstruction algorithm for signal recovery from 2-level amplitude sampling is proposed. Our method is non-iterative and exploits high fidelity local signal approximation properties of special, numerically robust differential operators known as chromatic derivatives and the associated chromatic signal expansions. Al...

Online rating systems are widely accepted as means for quality assessment on the web and users increasingly rely on these systems when deciding to purchase an item online. This makes such rating systems frequent targets of attempted manipulation by posting unfair rating scores. Therefore, providing useful, realistic rating scores as well as detecti...

Trust and privacy in social participatory sensing systems have always been challenging issues. Trust and privacy are somehow interconnected and interdependent concepts, and solutions that take into account both of these two parameters simultaneously will result in better people evaluation in the context of social participatory networks. In this pap...

Chromatic derivatives are special, numerically robust differential operators which preserve spectral features of a signal; the associated chromatic approximations accurately capture local features of a signal. For this reason they allow digital processing of continuous time signals often superior to processing of discrete samples of such signals. W...

Chromatic derivatives are special, numerically robust differential operators which preserve spectral features of a signal; the associated chromatic approximations accurately capture local features of a signal. In the first part of this paper, entitled Chromatic Derivatives and Approximations in Practice (I): A General Framework, we have derived a c...

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 co...

In a recent paper, the first author considered orthonormal polynomials \(\left \{p_{n}\right \}\) associated with a symmetric measure with unbounded support and with recurrence relation $$\displaystyle{ xp_{n}\left (x\right ) = A_{n}p_{n+1}\left (x\right ) + A_{n-1}p_{n-1}\left (x\right ),\quad n \geq 0. }$$ Under appropriate restrictions on \(\lef...

With the advancement in electronics technology, number of pins under the ball grid array (BGA) are increasing on reduced size components. In small size components, a challenging task is to solve the escape routing problem where BGA pins escape towards the component boundary. It is often desirable to perform ordered simultaneous escape routing (SER)...

Motivation: The Variant Call Format (VCF) is widely used to store data about genetic variation. Variant calling workflows detect potential variants in large numbers of short sequence reads generated by DNA sequencing and report them in VCF format. To evaluate the accuracy of variant callers, it is critical to correctly compare their output against...

We characterise asymptotic behaviour of families of symmetric orthonormal polynomials whose recursion coefficients satisfy certain conditions, satisfied for example by the (normalised) Hermite polynomials. More generally, these conditions are satisfied by the recursion coefficients of the form for and , as well as by recursion coefficients which co...

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...

VLSI systems often rely on embedded cryptographic cores for security when the confidentiality and authorization is a must. Such cores are theoretically sound but often vulnerable to physical attacks like side-channel analysis (SCA). Several countermeasures have been previously proposed to protect these cryptographic cores. QuadSeal was proposed as...

We consider the problem of data collection from a continental-scale network of energy harvesting sensors, applied to tracking mobile assets in rural environments. Our application constraints favour a highly asymmetric solution, with heavily duty-cycled sensor nodes communicating with powered base stations. We study a novel scheduling optimisation p...

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 consider the risk propagation among risky hosts and flows. In this paper, this is achieved by introducing two novel concepts. First, an interdependency relationship among the...

The need for Multiprocessor Systems-on-Chip (MPSoCs) to satisfy performance demands of applications in embedded systems has enabled vendors to create different communication architectures for MPSoCs. It is a challenge to rapidly identify the best communication architecture and its best configuration, in terms of task mapping and buffer size, for a...

The paper presents a novel Wi-Fi fingerprinting system CSI-MIMO that uses a fine-grained information known as Channel State Information (CSI). The proposed CSI-MIMO exploits the frequency diversity and spatial diversity using Multiple Input Multiple Output (MIMO) system. The proposed CSI-MIMO uses either magnitude or complex CSI based on the mobili...

Online rating systems are widely accepted as a means for quality assessment on the web, and users increasingly rely on these systems when deciding to purchase an item online. This fact motivates people to manipulate rating systems by posting unfair rating scores for fame or profit. Therefore, both providing useful realistic rating scores as well as...

Trust and reputation systems are widely employed in WSNs to help decision making processes by assessing trustworthiness of sensors as well as the reliability of the reported data. Iterative filtering (IF) algorithms hold great promise for such a purpose; they simultaneously estimate the aggregate value of the readings and assess the trustworthiness...

We characterise asymptotic behaviour of families of symmetric orthonormal polynomials whose recursion coefficients satisfy certain conditions, satisfied for example by the (normalised) Hermite polynomials and, more generally, by families with recursion coefficients of the form c(n+1)^p for 0 < p < 1 and c > 0. We use this result to show that, in a...

Due to limited computational power and energy resources, aggregation of data from multiple sensor nodes done at the aggregating node is usually accomplished by simple methods such as averaging. However such aggregation is known to be highly vulnerable to node compromising attacks. Since WSN are usually unattended and without tamper resistant hardwa...

This concludes our brief summary of the cyclic trust computation framework proposed in Lim et al. (2010).In Lim et al. (2012) the authors have proposed a game-theoretical defence strategyto protect sensor nodes from attacks and to guarantee ahigher level of trustworthiness for sensed data. However, such approach can be compromised with collusive (c...

Advanced Encryption Standard (AES) is arguably the most popular symmetric block cipher algorithm. The commonly used mode of operation in AES is the Electronic Codebook (ECB) mode. In the past, side channel attacks (including power analysis based attacks) have been shown to be effective in breaking the secret keys used with AES, while AES is operati...

We characterise asymptotic behaviour of families of orthonormal polynomials whose recursion coefficients satisfy certain conditions, satisfied for example by the Hermite polynomials and, more generally, by families with recursion coefficients of the form c(n+1)^p for 0<p<1. We use this result to show that, in a Hilbert space associated with a famil...

Wi-Fi based fingerprinting systems, mostly utilize the Received Signal Strength Indicator (RSSI), which is known to be unreliable due to environmental and hardware effects. In this paper, we present a novel Wi-Fi fingerprinting system, exploiting the fine-grained information known as Channel State Information (CSI). The frequency diversity of CSI c...

The paradigm of pipelined MPSoC (processors connected in a pipeline) is well suited to data flow nature of multimedia applications. Often design space exploration is performed to optimize execution time, latency or throughput of a pipelined MPSoC where the variants in the system are processor configurations due to customizable options in each of th...

Detection of high risk network flows and high risk hosts is becoming ever more important and more challenging. In order to selectively apply deep packet inspection (DPI) one has to isolate in real time high risk network activities within a huge number of monitored network flows. To help address this problem, we propose an iterative methodology for...

Low-power compact sensor nodes are being increasingly used to collect trajectory data from moving objects such as wildlife. The size of this data can easily overwhelm the data storage available on these nodes. Moreover, the transmission of this extensive data over the wireless channel may prove to be difficult. The memory and energy constraints of...

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 heav-ily duty-cycled sensor nodes communicating with a network of powered base stations. Individual nodes move freely in the environment, resul...

In this paper we introduce a novel sophisticated collusion attack scenario against a number of existing iterative filtering algorithms. To address this security issue, we propose an improvement for iterative filtering techniques by providing an initial approximation for such algorithms which makes them not only collusion robust, but also more accur...

This paper studies the effects of last-level cache on DRAM energy consumption. In particular, we explore how different last-level cache configurations affect the idle periods of DRAM, and whether those idle periods can be exploited through the use of self refresh power down mode to enable maximum energy reduction in both the energy consumption of t...

Intermittent faults (IF) in chips are becoming commonplace with the current technology trend and the process scaling. In this paper, we first modify the well known birth-death Markov model so that availability can be calculated. We then show that the standard birth-death Markov model does not capture IF correctly, and create a novel Markov model fo...

Discovering high risk network flows and hosts in a high throughput network is a challenging task of network monitoring. Emerging complicated attack scenarios such as DDoS attacks increase the complexity of tracking malicious and high risk network activities within a huge number of monitored network flows. To address this problem, we propose an iter...

As a new distributed computing model, crowdsourcing lets people leverage the crowd's intelligence and wisdom toward solving problems. This article proposes a framework for characterizing various dimensions of quality control in crowdsourcing systems, a critical issue. The authors briefly review existing quality-control approaches, identify open iss...

Social rating systems are widely used to harvest user feedback and to support making decisions by users on the Web. Web users may try to exploit such systems by posting unfair or false evaluations for fame or profit reasons. Detecting the real rating scores of products as well as the trustworthiness of reviewers is an important and a very challengi...

Social rating systems are subject to unfair evaluations. Users may try to individually or collaboratively promote or demote a product. Detecting unfair evaluations, mainly massive collusive attacks as well as honest looking intelligent attacks, is still a real challenge for collusion detection systems. In this paper, we study the impact of unfair e...

Online rating systems are subject to unfair evaluations. Users may try to individually or collaboratively promote or demote a product. Collaborative unfair rating, i.e., collusion, is more damaging than individual unfair rating. Detecting massive collusive attacks as well as honest looking intelligent attacks is still a real challenge for collusion...

Worker selection is a significant and challenging issue in crowdsourcing systems. Such selection is usually based on an assessment of the reputation of the individual workers participating in such systems. However, assessing the credibility and adequacy of such calculated reputation is a real challenge. In this paper, we propose an analytic model w...

In this paper we introduce an iterative voting algorithm and then use it to obtain a rating method which is very robust against collusion attacks as well as random and biased raters. Unlike the previous iterative methods, our method is not based on comparing submitted evaluations to an approximation of the final rating scores, and it entirely decou...

Online rating systems are subject to malicious behaviors mainly by posting unfair rating scores. Users may try to individually or collaboratively promote or demote a product. Collaborating unfair rating 'collusion' is more damaging than individual unfair rating. Although collusion detection in general has been widely studied, identifying collusion...

Multiprocessor System-on-Chip (MPSoC) is an integral element in state-of-the-art embedded devices, ranging from low-end, mobile phones, PDAs, handheld medical devices up to high-end cars, avionics and robotics. Proper and safe functionality of such embedded systems is mandatory to avoid severe consequences, whereas security is absolutely necessary...

Worker selection is a significant and challenging issue in crowdsourcing systems. Such selection is usually based on an assessment of the reputation of the individual workers participating in such systems. However, assessing the credibility and adequacy of such calculated reputation is a real challenge. In this paper, we propose a reputation manage...

Chromatic derivatives and series expansions of bandlimited func-tions have recently been introduced as an alternative representation to the Taylor series, and they have been shown to be more useful in practical signal processing applications than in the Taylor series. Although chromatic series were originally introduced for bandlimited functions, t...

Embedded systems are ubiquitous and are utilised for secure transactions. It is apparent that cashless wallets are the only future forward as handheld devices are already popular for payments. Side channel attacks are a significant threat to the deployment of secure embedded systems. Differential Power Analysis is one of the powerful power analysis...

Side channel attackers observe external manifestations of internal computations in an embedded system to predict the encryption key employed. The ability to examine such external manifestations (power dissipation or electromagnetic emissions) is a major threat to secure embedded systems. This study proposes a secure multiprocessor architecture to p...

Estimation models play a vital role in many aspects of day to day life. Extremely complex estimation models are employed in the design space exploration of SoCs, and the efficacy of these estimation models is usually measured by the absolute error of the models compared to known actual results. Such absolute error based metrics can often result in...

This paper describes a rapid design methodology to create a pipeline of processors to execute streaming applications. The methodology seeks a system with the smallest area while its runtime is within a specified runtime constraint. Initially, a heuristic is used to rapidly explore a large number of processor configurations to find the near Pareto f...

Given a band limited signal which over some disjoint intervals of time I_n behaves as a corresponding linear combination f_n(t) of up to N damped sinusoids, we present a method which detects intervals I_n, determines the number of the sinusoidal components over each interval and estimates their frequencies, with high a...

A streaming application, characterized by a kernel that can be broken down into independent tasks which can be executed in a pipelined fashion, inherently allows its implementation on a pipeline of Application Specific Instruction set Processors (ASIPs), called a pipelined MPSoC. The latency and throughput requirements of streaming applications put...

We consider the problem of on-chip L2 cache management and replacement policies. We propose a new adaptive cache replacement policy, called Dueling CLOCK (DC), that has several advantages over the Least Recently Used (LRU) cache replacement policy. LRU's strength is that it keeps track of the 'recency' information of memory accesses. However, a) LR...

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...

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 p...

Standard approaches to evaluating and comparing information retrieval systems compute simple averages of performance statistics across individual topics to measure the overall system performance. However, topics vary in their ability to differentiate among systems based on their retrieval performance. At the same time, systems that perform well on...

We present a detailed motivation for the notions of chromatic derivatives and chromatic expansions. Chromatic derivatives are special, numerically robust linear differential operators; chromatic expansions are the associated local expansions, which possess the best features of both the Taylor and the Nyquist expansions. We give a simplified treatme...

This paper presents the basic properties of chromatic derivatives and chromatic expansions and provides an appropriate motivation for introducing these notions. Chromatic derivatives are special, numerically robust linear differential operators which correspond to certain families of orthogonal polynomials. Chromatic expansions are series of the co...

A heterogeneous multi-pipeline architecture to enable high-performance application-specific instruction-set processor (ASIP) design is proposed. Each pipeline in this architecture is extensively customised. The program instruction-level parallelism is statically explored during compilation. Techniques such as forwarding network reduction, instructi...

Agents from a community interact in pairwise transactions across discrete time. Each agent reports its evaluation of another agent with which it has just had a transaction to a central system. This system uses these time-sequences of experience evaluations to infer how much the agents trust each another. Our paper proposes rationality assumptions (...

In this paper, we present a novel HitME (Hit-MEmory) buffer to reduce the energy consumption of memory hierarchy in embedded processors. The HitME buffer is a small direct-mapped cache memory that is added as additional memory into existing cache memory hierarchies. The HitME buffer is loaded only when there is a hit on L1 cache. Otherwise, L1 cach...

Community Question Answering (cQA) services, such as Yahoo! Answers and MSN QnA, facilitate knowledge sharing through question answering by an online community of users. These services include incentive mechanisms to entice participation and self-regulate the quality of the content contributed by the users. In order to encourage quality contributio...

Side channel attack based upon the analysis of power traces is an effective way of obtaining the encryption key from secure processors. Power traces can be used to detect bitflips which betray the secure key. Balancing the bitflips with opposite bitflips have been proposed, by the use of opposite logic. This is an expensive solution, where the bala...

Side channel attacks are a significant threat to the deployment of secure embedded systems. Differential power analysis is one of the powerful power analysis attacks, which can be exploited in secure devices such as smart cards, PDAs and mobile phones. Several researchers in the past have presented experiments and countermeasures for differential p...

Let M be a symmetric positive definite moment functional and let {PnM(w)}n Î \Bbb N\{P_n^{\cal M}(\omega)\}_{n\in {\Bbb N}} be the family of orthonormal polynomials that corresponds to M. We introduce a family of linear differential operators Kn = (-i)nPnM(i\fracddt){\cal K}^n =(-i)^nP_n^{\cal M}(i\frac{d}{dt}) , called the chromatic derivative...

Modern application specific instruction set processors (ASIPs) have customizable caches, where the size, associativity and line size can all be customized to suit a particular application. To find the best cache size suited for a particular embedded system, the applications) is/are executed, traces obtained, and caches simulated. Typically, program...

In our work on frequency estimation based on local signal behavior [the author; Frequency estimation using time domain methods based on local signal behavior. Manuscript (2010)] for testing purposes we needed a signal ϕ(t) which over some disjoint intervals of (continuous) time I n is equal to a corresponding linear combination f n (t) of up to N s...

Compression has long been utilized in electronic systems to improve performance, reduce transmission costs, and to minimize code size. In this chapter we show two separate techniques to compress instructions. The first technique compresses instruction traces, so that the compressed trace can be used to explore the best cache configuration to be use...

Small area and code size are two critical design issues in most of embedded system designs. In this paper, we tackle these issues by customizing forwarding networks and instruction encoding schemes for multi-pipe Application Specific Instruction-Set Processors (ASIPs). Forwarding is a popular technique to reduce data hazards in the pipeline to impr...

A method to both reduce energy and improve performance in a processor-based embedded system is described in this paper. Comprising of a scratchpad memory instead of an instruction cache, the target system dynamically (at runtime) copies into the scratchpad code segments that are determined to be beneficial (in terms of energy efficiency and/or spee...

Scratchpad memory has been introduced as a replacement for cache memory as it improves the performance of certain embedded systems. Additionally, it has also been demonstrated that scratchpad memory can significantly reduce the energy consumption of the memory hierarchy of embedded systems. This is significant, as the memory hierarchy consumes a su...

Modern embedded system execute a single application or a class of applications repeatedly. A new emerging methodology of designing embedded system utilizes configurable processors where the cache size, associativity, and line size can be chosen by the designer. In this paper, a method is given to rapidly find the L1 cache miss rate of an applicatio...

In this paper we devise some technical tools for dealing with problems connected with the philosophical view usually called mathematical instrumentalism. These tools are interesting in their own right, independently of their philosophical consequences. For example, we show that even though the fragment of Peano's Arithmetic known as IΣ₁ is a conser...