171 research outputs found
RIPP-FS: An RFID identification, privacy preserving protocol with forward secrecy
No full textThis paper presents a new RFID identification protocol: RIPP-FS. The proposed protocol is based on hash chains, and enforces privacy and forward secrecy. Further, unlike other protocols based on hash chains, our proposal is resilient to a specific DoS attack, in which the attacker attempts to exhaust the hash chain the tag is programmed to spend. The computations required on the tag side are very limited, just three hash functions; on the reader side RIPP-FS allows to leverage pre-computations, in such a way that tag identification resolves to a lookup in pre-computed tables, speeding up the identification process. To the best of our knowledge this is the first protocol providing all these features at once
eRIPP-FS: Enforcing Privacy and Security in RFID
No full textIn RFID systems addressing security issues, many authentication techniques require the tag to keep some sort of synchronization with the reader. In particular, this is true in those proposals that leverage hash chains. When the reader and the tag get de-synchronized, possibly by an attacker, this paves the way to several denial of service (DoS) attacks, as well as threatening privacy (e.g., via the timing attack). Even if de-synchronization happens for non-malicious causes, this event has a negative effect on performances (for instance, slowing down the authentication process). In this paper, we provide a solution to cope with the de-synchronization between the tag and the reader when hash chains are employed. In particular, our solution relies on mutual reader-tag authentication, achieved via hash traversal and Merkle tree techniques. We show that this techniques applied to an existing security protocol for RFID systems, such as RIPP-FS, make timing attacks hard to succeed. Moreover, the proposed solutions can be transparently and independently adopted by similar security protocols as well to thwart timing attack and/or to provide reader-tag mutual authentication. Finally, extensive simulations show that our proposal introduces a negligible overhead to recover desynchronization. © 2009 John Wiley & Sons, td
Nuovi spazi tra città, parco e infrastruttura. Progetto di riuso creativo per l'ex ospedale Sant'Anna Como
No full textLAUREA MAGISTRALELa tesi di laurea affronta il tema della rigenerazione, del riuso e della valorizzazione di una vasta area della città di Como, fino a qualche anno fa sede del maggiore ospedale cittadino.
Un progetto innovativo per l’ex Sant’Anna può diventare motore di una ridefinizione complessiva dei caratteri del contesto.
La strategia fisico-spaziale mira ad una ridefinizione “creativa” della vocazione e dei caratteri del luogo, attraversando le diverse scale del progetto mediante una diversa “intensità” di azione trasformativa sull’esistente.
Dato l’assetto territoriale del luogo e dei suoi spazi aperti, è stato ritenuto importante perdere la percezione di recinto chiuso, per essere trasformato in quartiere urbano a servizio dei cittadini, pervaso dal verde, al fine di rappresentare a tutti gli effetti un luogo-cerniera capace di riunire i due tratti del Parco della Spina Verde, oggi separati.
La soluzione progettuale presenta un mix tra edifici recuperati e nuovi volumi: è stata mantenuta e resa riconoscibile l’assialità dell’impianto originario con il mantenimento delle corti ad U, del monoblocco e dei tre padiglioni fronte strada.
L’edificio esistente più alto e “massivo”, il cosiddetto monoblocco è - all’interno di un masterplan radicalmente trasformato – il settore di sperimentazione dell’intervento più innovativo con la conservazione unicamente della struttura esistente composta da travi e pilastri.
La creatività, termine molto dibattuto nella contemporaneità, si propone alle diverse scale del progetto come fattore chiave, alla base del binomio funzione-architettura.
L’integrazione tra edifici e spazi aperti concorre a definire una nuova centralità e un nuovo margine tra natura e costruito: uno spazio definito da funzioni prevalentemente pubbliche e nella quale convergono i principali flussi ciclopedonali.
Queste trasformazioni recepiscono un discorso più ampio di modifica infrastrutturale della città di Como, attraverso la proposta di metrotramvia veloce, sul tracciato attuale FNM,con stazioni più ravvicinate, tra le quali, un polo unico di interscambio con la linea FS, in prossimità del recente autosilo Val Mulini, in continuità con l’area di progetto
eRIPP-FS: Enforcing Privacy and Security in RFID
No full textIn RFID systems addressing security issues, many authentication techniques require the tag to keep some sort of synchronization with the reader. In particular, this is true in those proposals that leverage hash chains. When the reader and the tag get de-synchronized, possibly by an attacker, this paves the way to several denial of service (DoS) attacks, as well as threatening privacy (e.g., via the timing attack). Even if de-synchronization happens for non-malicious causes, this event has a negative effect on performances (for instance, slowing down the authentication process).
In this paper, we provide a solution to cope with the de-synchronization between the tag and the reader when hash chains are employed. In particular, our solution relies on mutual reader-tag authentication, achieved via hash traversal and Merkle tree techniques. We show that this techniques applied to an existing security protocol for RFID systems, such as RIPP-FS, make timing attacks hard to succeed. Moreover, the proposed solutions can be transparently and independently adopted by similar security protocols as well to thwart timing attack and/or to provide reader-tag mutual authentication.
Finally, extensive simulations show that our proposal introduces a negligible overhead to recover desynchronization
Effect of instrumental ESI-MS parameters on aluminium(III)-ligand solution equilibria
No full textElectrospray ionization mass spectrometry (ESI-MS) is being increasingly employed in the study of metal-ligand equilibria in aqueous solution [1, 2, 3]. In the present work, the ESI-MS spectral changes due to different settings of the following listed parameters are analysed: the solution flow rate (FS), the nebulizer gas flow rate (FG), the sprayer potential (E), and the temperature of the counter-current gas flow (T). 28 spectra were obtained for each of six samples containing aluminium(III) and 1,6 dimethyl 4 hydroxy 3 pyridincarboxylic acid at various pH, in the absence or in presence of a buffer, triethylamine, and acetic acid. The abundance of relevant ions were fitted versus the value s of FS, FG, E and T. Most of ionic intensities were significantly related to these instrumental parameters. Correlations were interpreted considering the presence of three kinds of perturbations occurring in the ESI ion source: formation of dimers in the droplets, different transfert efficiency from the gas phase for different complexes (according to their surface activity), and subsequent partial thermal decomposition of dimers and of some of the complexes in the gas phase.
Our results show that the evaluation of the effects produced in the ESI-MS spectra by a change of instrumental parameters can allow to identify the perturbation occurring when metal-ligand solutions are studied by ESI-MS.
References:
[1] Valerio B. Di Marco et al., Mass Spectrometry Reviews, 2006; 25, 347-379.
[2] Ray Colton et al., Mass Spectrometry Reviews, 1995; 14, 79-106.
[3] Valerio B. Di Marco et al., Journal of Mass Spectrometry, 2009; 4, 120-127
RIPP-FS: an RFID Identification, Privacy Preserving protocol with Forward Secrecy
No full textThis paper presents a new RFID identification protocol:
RIPP-FS. The proposed protocol is based on hash chains
and it enforces privacy and forward secrecy. Further, un-
like other protocols based on hash chains, our proposal is
resilient to a specific DoS attack, in which the attacker at-
tempts to exhaust the hash chain the tag is programmed to
spend. The computations required on the tag side are very
limited, just three hash functions; on the reader side RIPP-
FS allows to leverage pre-computations, in such a way that
tag identification resolves to a lookup in pre-computed ta-
bles, speeding up the identification process. To the best of
our knowledge this is the first protocol providing all these
features at once
FastRIPP: RFID Privacy Preserving protocol with Forward Secrecy and Fast Resynchronization.
No full textIn the next future Radio Frequency IDentification
(RFID) systems will be so pervasive that everyone will wear
(maybe unawares) a kit of personal tags. However, a major con-
cern that prevents a wide diffusion of this emerging technology is
privacy. Several proposed protocols try to solve the privacy issue,
but are exposed to many others security flaws, such as denial of
service or lack of forward secrecy. One recently proposed solution
addressing all these problems is RIPP-FS: an RFID identification
protocol that guarantees privacy, authentication and forward
secrecy, allowing the reading of many tags at once. While efficient,
RIPP-FS requires some extra computations on the tag side when
a tag misses several consecutive queries from the reader.
In this paper we propose FastRIPP, an efficient protocol that
significantly reduces the exposed overhead. This improvement is
inspired by an efficient hash traversal amortization technique
that uses fractal hash sequence representation. We analyzed
the performances of the proposed protocol compared with the
original version of RIPP-FS. The results of extensive simulations
confirm the gain of performance of the proposed protocol. Finally,
note that the proposed solution could be adopted by other RFID
identification protocols as well
Dynamic bias and jitter reduction in a highly linear Digital-to-Time Converter for digital PLLs in 28nm CMOS technology
No full textLAUREA MAGISTRALEL'obiettivo della tesi è di migliorare le performance di rumore di un'esistente architettura di Digital-to-Time Converter (DTC) ad alta linearità, con lo scopo di rendere realizzabili PLL digitali ad alta purezza spettrale e basso rumore. L'architettura di riferimento, infatti, mostra un non linearità integrata (INL) misurata di 80 fs su un range di 246 ps, che costituisce una delle migliori performance in letteratura, permettendo spurie frazionarie minori di -64 dBc all'uscita del PLL. Tuttavia, lo stesso non vale per il rumore. Il rumore di fase di un PLL, infatti, è tipicamente dominato dal contributo del DTC; di conseguenza una riduzione di quest'ultimo è obbligatoria al fine di ottenere PLL a basso rumore. Dopo un'analisi accurata delle sorgenti di non linearità e di rumore nell'architettura di riferimento, andremo a mostrare un limitante trade-off tra INL e jitter. La prima soluzione proposta è l'utilizzo di resistenze per sostituire i generatori di corrente; tuttavia questo porta ad una enorme e distruttiva sensitività all'alimentazione. Dato che un'istantanea stabilizzazione di quest'ultima (per esempio attraverso un LDO) porta ad un grande consumo di potenza, viene proposto un approccio differente e tecniche di alimentazione dinamica verranno investigate. Andremo ad illustrare un utile meccanismo di cancellazione di rumore proprio della nostra architettura e, infine, andremo a mostrare l'implementazione fisica del DTC. In definitiva, la simulazione post-layout mostra una INL di 170 fs su un range di 230 fs, col modello del peggior caso di bonding incluso. Il rumore di fase risulta essere -159.17 dBc/Hz a 1 MHz di offset e 250 MHz di frequenza di funzionamento, il che vuol dire una riduzione di 11.27 dB rispetto all'architettura di riferimento, mentre il jitter integrato da 1 KHz a 125 MHz risulta essere 89 fs. Per concludere, il nostro DTC sembra avere, da simulazione, la migliore performance in termini di trade-off tra INL e jitter rispetto agli altri lavori presenti in letteratura.The goal of the thesis is to improve the noise performance of an already existing high-linearity Digital-to-Time Converter (DTC) architecture, with a view to making high-spectral-purity and low-noise digital PLLs something feasible. The reference architecture, in fact, shows a measured integral-non-linearity (INL) of 80 fs over a range of 246 ps, which is one of the best performance in literature, allowing for less than -64 dBc fractional spurs at the PLL output. However, this is not the same for what concerns the noise. The phase-noise of a PLL, in fact, is typically dominated by the DTC contribution; therefore, a reduction of the latter is mandatory for low-noise PLLs. After an in-depth analysis of the non-linearity and noise sources in the reference architecture, we are going to show a limiting trade-off between INL and jitter. The first proposed solution is the usage of resistors to substitute current generators; however this comes with a detrimental huge sensitivity to the supply. Since an instantaneous stabilization of the latter (e.g., with an LDO) comes with a very large power dissipation, a different approach is proposed and dynamic supply biasing techniques will be investigated. We are going to illustrate a useful noise-cancelling mechanism of our architecture and, finally, we're going to show the DTC physical implementation. Ultimately, post-layout simulation shows an INL of 170 fs over a range of 230 fs, with modelling of the worst-case bonding included. Phase-noise turns out to be -159.17 dBc/Hz @ 1 MHz offset and 250 MHz operating frequency, meaning a reduction of 11.27 dB w.r.t. the reference architecture, while the integrated jitter from 1 KHz to 125 MHz results to be 89 fs. In conclusion, our DTC seems to have, by simulations, the best performance in terms of trade-off between INL and jitter with respect to the other works present in literature
Role of frozen section associated with intraoperative cytology in comparison to FNA and FS alone in the management of thyroid nodules
No full textAbstract
AIMS: The utilization of fine needle aspiration (FNA) biopsy is an accurate and cost-effective method in the diagnosis of thyroid diseases. However, the non-diagnostic cases and cases of suspicious carcinoma remain a dilemma, and in these cases thyroidectomy is usually recommended, even if only 15-20% of these patients really need a thyroidectomy. To avoid unnecessary surgical treatment, frozen section (FS) is usually performed. This method is well recognized, but is not useful for the diagnosis of follicular lesions. Therefore, many authors have tried to increase the specificity and sensibility of intraoperative examination, supporting it with an intraoperative cytological technique (IC). To clarify the role of intraoperative exam (FS and IC), also comparing to FNA, we have reviewed our own experiences.
METHODS: In a period covering 6 years (2000-2005), FS was performed in 1,472 cases out of 11,420 total thyroidectomy operations. FS diagnosis and definitive diagnosis, were reviewed and confirmed, moreover, FNA diagnosis and definitive diagnosis were also considered and all intraoperatory cytological slides were reviewed. Diagnostic accuracy was assessed for FNA and FS with or without intraoperative cytology. We compared 1,472 FS diagnoses with their definitive histological diagnosis; 728 FNA out of 1,472 patients with definitive histological diagnosis, and 564 FS associated with IC out of 1,472 patients with definitive diagnosis.
RESULTS: The diagnostic accuracy of these three methods were, respectively, 88.8%, 88.8% and 95.7%.
CONCLUSION: We can assert that FS associated with IC remains the most accurate technique in the surgical management of thyroid nodules
Get in touch with calculus: a new material device collecting a historical legacy
No full textWe introduce an analog device designed for laboratory activities related to calculus. Such
a device recollects the legacy of historical instruments to find the area by solving inverse
tangent problems (integraphs), that analytically corresponds to the resolution of differential
equations. We present an analysis of its exploration by a high-school mathematical
teacher with experience in mathematical machines
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