12,866 research outputs found
Biometric Backdoors: A Poisoning Attack Against Unsupervised Template Updating
In this work, we investigate the concept of biometric backdoors: a template
poisoning attack on biometric systems that allows adversaries to stealthily and
effortlessly impersonate users in the long-term by exploiting the template
update procedure. We show that such attacks can be carried out even by
attackers with physical limitations (no digital access to the sensor) and zero
knowledge of training data (they know neither decision boundaries nor user
template). Based on the adversaries' own templates, they craft several
intermediate samples that incrementally bridge the distance between their own
template and the legitimate user's. As these adversarial samples are added to
the template, the attacker is eventually accepted alongside the legitimate
user. To avoid detection, we design the attack to minimize the number of
rejected samples.
We design our method to cope with the weak assumptions for the attacker and
we evaluate the effectiveness of this approach on state-of-the-art face
recognition pipelines based on deep neural networks. We find that in scenarios
where the deep network is known, adversaries can successfully carry out the
attack over 70% of cases with less than ten injection attempts. Even in
black-box scenarios, we find that exploiting the transferability of adversarial
samples from surrogate models can lead to successful attacks in around 15% of
cases. Finally, we design a poisoning detection technique that leverages the
consistent directionality of template updates in feature space to discriminate
between legitimate and malicious updates. We evaluate such a countermeasure
with a set of intra-user variability factors which may present the same
directionality characteristics, obtaining equal error rates for the detection
between 7-14% and leading to over 99% of attacks being detected after only two
sample injections.Comment: 12 page
Thalamo-cortical network activity between migraine attacks. Insights from MRI-based microstructural and functional resting-state network correlation analysis
BACKGROUND:
Resting state magnetic resonance imaging allows studying functionally interconnected brain networks. Here we were aimed to verify functional connectivity between brain networks at rest and its relationship with thalamic microstructure in migraine without aura (MO) patients between attacks.
METHODS:
Eighteen patients with untreated MO underwent 3 T MRI scans and were compared to a group of 19 healthy volunteers (HV). We used MRI to collect resting state data among two selected resting state networks, identified using group independent component (IC) analysis. Fractional anisotropy (FA) and mean diffusivity (MD) values of bilateral thalami were retrieved from a previous diffusion tensor imaging study on the same subjects and correlated with resting state ICs Z-scores.
RESULTS:
In comparison to HV, in MO we found significant reduced functional connectivity between the default mode network and the visuo-spatial system. Both HV and migraine patients selected ICs Z-scores correlated negatively with FA values of the thalamus bilaterally.
CONCLUSIONS:
The present results are the first evidence supporting the hypothesis that an abnormal resting within networks connectivity associated with significant differences in baseline thalamic microstructure could contribute to interictal migraine pathophysiology
An Evaluation of Score Level Fusion Approaches for Fingerprint and Finger-vein Biometrics
Biometric systems have to address many requirements, such as large population
coverage, demographic diversity, varied deployment environment, as well as
practical aspects like performance and spoofing attacks. Traditional unimodal
biometric systems do not fully meet the aforementioned requirements making them
vulnerable and susceptible to different types of attacks. In response to that,
modern biometric systems combine multiple biometric modalities at different
fusion levels. The fused score is decisive to classify an unknown user as a
genuine or impostor. In this paper, we evaluate combinations of score
normalization and fusion techniques using two modalities (fingerprint and
finger-vein) with the goal of identifying which one achieves better improvement
rate over traditional unimodal biometric systems. The individual scores
obtained from finger-veins and fingerprints are combined at score level using
three score normalization techniques (min-max, z-score, hyperbolic tangent) and
four score fusion approaches (minimum score, maximum score, simple sum, user
weighting). The experimental results proved that the combination of hyperbolic
tangent score normalization technique with the simple sum fusion approach
achieve the best improvement rate of 99.98%.Comment: 10 pages, 5 figures, 3 tables, conference, NISK 201
Practical Improvements of Profiled Side-Channel Attacks on a Hardware Crypto-Accelerator
Abstract. This article investigates the relevance of the theoretical frame-work on profiled side-channel attacks presented by F.-X. Standaert et al. at Eurocrypt 2009. The analyses consist in a case-study based on side-channel measurements acquired experimentally from a hardwired crypto-graphic accelerator. Therefore, with respect to previous formal analyses carried out on software measurements or on simulated data, the inves-tigations we describe are more complex, due to the underlying chip’s architecture and to the large amount of algorithmic noise. In this dif-ficult context, we show however that with an engineer’s mindset, two techniques can greatly improve both the off-line profiling and the on-line attack. First, we explore the appropriateness of different choices for the sensitive variables. We show that a skilled attacker aware of the regis-ter transfers occurring during the cryptographic operations can select the most adequate distinguisher, thus increasing its success rate. Sec-ond, we introduce a method based on the thresholding of leakage data to accelerate the profiling or the matching stages. Indeed, leveraging on an engineer’s common sense, it is possible to visually foresee the shape of some eigenvectors thereby anticipating their estimation towards their asymptotic value by authoritatively zeroing weak components containing mainly non-informational noise. This method empowers an attacker, in that it saves traces when converging towards correct values of the secret. Concretely, we demonstrate a 5 times speed-up in the on-line phase of the attack.
Verifying Security Properties in Unbounded Multiagent Systems
We study the problem of analysing the security for an unbounded number of concurrent sessions of a cryptographic protocol. Our formal model accounts for an arbitrary number of agents involved in a protocol-exchange which is subverted by a Dolev-Yao attacker. We define the parameterised model checking problem with respect to security requirements expressed in temporal-epistemic logics. We formulate sufficient conditions for solving this problem, by analysing several finite models of the system. We primarily explore authentication and key-establishment as part of a larger class of protocols and security requirements amenable to our methodology. We introduce a tool implementing the technique, and we validate it by verifying the NSPK and ASRPC protocols
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