Analysis of adversarial attacks against CNN-based image forgery detectors

With the ubiquitous diffusion of social networks, images are becoming a dominant and powerful communication channel. Not surprisingly, they are also increasingly subject to manipulations aimed at distorting information and spreading fake news. In recent years, the scientific community has devoted major efforts to contrast this menace, and many image forgery detectors have been proposed. Currently, due to the success of deep learning in many multimedia processing tasks, there is high interest towards CNN-based detectors, and early results are already very promising. Recent studies in computer vision, however, have shown CNNs to be highly vulnerable to adversarial attacks, small perturbations of the input data which drive the network towards erroneous classification. In this paper we analyze the vulnerability of CNN-based image forensics methods to adversarial attacks, considering several detectors and several types of attack, and testing performance on a wide range of common manipulations, both easily and hardly detectable

Do GANs leave artificial fingerprints?

In the last few years, generative adversarial networks (GAN) have shown tremendous potential for a number of applications in computer vision and related fields. With the current pace of progress, it is a sure bet they will soon be able to generate high-quality images and videos, virtually indistinguishable from real ones. Unfortunately, realistic GAN-generated images pose serious threats to security, to begin with a possible flood of fake multimedia, and multimedia forensic countermeasures are in urgent need. In this work, we show that each GAN leaves its specific fingerprint in the images it generates, just like real-world cameras mark acquired images with traces of their photo-response non-uniformity pattern. Source identification experiments with several popular GANs show such fingerprints to represent a precious asset for forensic analyses

Al2O3/ZrO2/Y3Al5O12 composites. A high-temperature mechanical characterization

An Al2O3/5 vol%·ZrO2/5 vol%·Y3Al5O12 (YAG) tri-phase composite was manufactured by surface modification of an alumina powder with inorganic precursors of the second phases. The bulk materials were produced by die-pressing and pressureless sintering at 1500 °C, obtaining fully dense, homogenous samples, with ultra-fine ZrO2 and YAG grains dispersed in a sub-micronic alumina matrix. The high temperature mechanical properties were investigated by four-point bending tests up to 1500 °C, and the grain size stability was assessed by observing the microstructural evolution of the samples heat treated up to 1700 °C. Dynamic indentation measures were performed on as-sintered and heat-treated Al2O3/ZrO2/YAG samples in order to evaluate the micro-hardness and elastic modulus as a function of re-heating temperature. The high temperature bending tests highlighted a transition from brittle to plastic behavior comprised between 1350 and 1400 °C and a considerable flexural strength reduction at temperatures higher than 1400 °C; moreover, the microstructural investigations carried out on the re-heated samples showed a very limited grain growth up to 1650 °C

Nanostructured nickel film deposition on carbon fibers for improving reinforcement-matrix interface in metal matrix composites

The issues in dispersing any form of carbon in metal matrix is the major problem in the field of metal matrix composites with carbon reinforcement (MMCcr). The low wettability of carbon in molten metals and the difference in density are some of the difficulties to obtain a good dispersion of carbon fibers in the matrix and, as a consequence, an improvement of some critical properties for metals in a wide range of application (mechanical properties, electrical properties, optical properties). For this reason, the aim of this work is to obtain a metallic coated carbon fiber to enhance the interaction between the reinforcement and the matrix. Moreover, also the density of carbon fibers could be adjusted depending on the thickness of the coating. Electroless Nickel-Phosphorus Plating (ENP) is one of the candidate to be a coating technique to improve the interaction between the carbon fibers and the metal matrix. Despite of its versatility in terms of complex geometry of the substrate and homogeneity and adhesion of the coating, the presence of the phosphorus in the alloy could create some problems with the metal matrix such as the formation of metal-phosphorus products that can drastically decrease the mechanical properties of the composite. For this reason, in this work, is presented a new way of Electroless Pure Nickel Plating (EPP) without any introduction of phosphorus in the nickel coating. The dependence of the coating thickness and the density of the coated fibers were studied under different plating parameters (temperature of the plating solution, deposition rate and plating solution composition). All the samples were characterized with SEM and XRD and the thickness, density and homogeneity were compared for all the samples obtained

Lightweight metallic matrix composites. Development of new composites material reinforced with carbon structures

Carbon nano/micro-structures used as fillers in metallic lightweight alloys matrix composites are receiving considerable attention in scientific research and industrial applications. Aluminum and magnesium are the most studied light metals used as matrices in metal composites materials principally for their low density (respectively 2.7 g/cm3 and 1.7 g/cm3) and low melting temperature (around 660 °C for both metals). A good interaction between matrix and fillers is the first step to obtain an increase in bulk properties; furthermore, the manufacturing procedure of the composite is fundamental in terms of quality of fillers dispersion. In this work the influence of surface modifications for three classes of carbon fillers for aluminum and magnesium alloy (AZ63) as matrices is studied. In particular, the selected fillers are short carbon micro fibres (SCMFs), carbon woven fabrics (CWF) and unidirectional yarn carbon fibres (UYFs). The surface modification was carried out by a direct coating of pure nickel on fibres. The electroless pure nickel plating was chosen as coating technique and the use of hydrazine as reducing agent has prevented the co-deposition of other elements (such as P or B). SEM and EDS analyses were performed to study the effect of surface modifications. The mechanical properties of manufactured composites were evaluated by four point flexural tests according to ASTM C1161 (room temperature). Results confirm improved interactions between matrix and fillers, and the specific interaction was studied for any chosen reinforcement

Static and dynamic weighing of rolling stocks by mean of a customized FBG-Sensorized-Patch

The structural health monitoring (SHM) of an infrastructure is of fundamental importance for the structure and people safety. Fiber Bragg Grating (FBG) sensors allow to design for each application, a tailored array of quasi-distributed sensors integrated to the infrastructure. To ensure the structural integrity of the railways is crucial to verify that the infrastructures comply with safety requirements to carry out their task. Railways rolling stock must comply with speed limits, the maximum number of wagons, maximum weight limit distributed on each axis of the wagons and the allowed number of trains on specific routes. The identification of the vertical load acting on each wheel is fundamental for the safety of a rolling-stock moving on a railway line. This paper presents the results of a test campaign on sensitive smart patches for static and dynamic weighing of trains. The system aims to generate a gripping system based on the magnetic force of a plastoferrite patch, taking advantage of the peculiarity that the rails are made of ferritic steel. This solution has the benefit of simplifying and speeding up the installation process and enabling a fast and easy removal or change in the configuration of the sensors array on the rail

Rivestimenti termospruzzati per barriere termiche di nuova concezione

Nel progetto di Dottorato presentato è stata ideata e presentata una innovativa configurazione multistrato di TPS di questo tipo, potenzialmente idonea sia ad un’applicazione in ambito propulsivo (rivestimento di palettature di turbine, camere di combustione, ugelli), sia come protezione termica per veicoli da rientro riutilizzabili. L’articolazione concettuale del lavoro è riassunta nello schema seguente: i.) dapprima una fase preliminare volta a verificare la realizzabilità del sistema ideato; ii.) quindi una estesa campagna di produzione e caratterizzazione dei materiali componenti del sistema per valutarne le proprietà, specie al variare della temperatura; iii.) il database dei materiali così realizzato viene utilizzato per una campagna di simulazione numerica necessaria da un lato a ottimizzare la struttura del sistema, dall’altro a valutarne le prestazioni in condizioni simili a quelle di esercizio; iv.) gli output delle fasi ii e iii vengono usati per individuare, produrre e testare materiali più performanti rispetto a quelli della fase ii; v.) viene prodotto il sistema aggiornato, realizzato con il patrimonio di conoscenze teoriche, sperimentali e simulative delle fasi precedenti. Il lavoro esposto ha riguardato la progettazione e realizzazione di un sistema TPS di nuova generazione. Allo stato attuale non sono ancora presenti sistemi di questo tipo nel panorama commerciale, altre proposte, a livello di ricerca accademica, vanno nella stessa direzione, ma non sono ancora mature. La fase di caratterizzazione, quella più impegnativa in termini di tempo e di risorse economiche, si è praticamente conclusa per quanto riguarda i materiali “standard”. Alcune delle caratterizzazioni eseguite per i materiali termospruzzati (segnatamente le prove meccaniche ad alta temperatura), sono di rarissima se non di nessuna presenza in letteratura, rappresentando di per sé un discreto valore scientifico. Per alcuni componenti, come il sistema Mo-Si-B, lo studio è in una fase più arretrata, pur avendo già consentito di mettere a punto parte dei processi produttivi, preliminari alle future fasi di preparazione delle polveri e termodeposizione. Anche lo studio relativo alla realizzazione di zirconati di cerio e lantanio ha dato discreti frutti, consentendo di mettere a punto tutto il processo di realizzazione, dalle polveri commerciali, fino al rivestimento vero e proprio, consentendo anche di realizzare i campioni spessi per le prove meccaniche ad alta T. Anche in questo caso non sono tuttora disponibili sul mercato produttori di polveri idonee alla produzione di questi materiali, obbligando a realizzare, come detto, tutto il processo. Il tema più controverso dell’attività, soprattutto sperimentale, è quello relativo alla caratterizzazione del molibdeno termospruzzato: purtroppo la sua estrema suscettibilità alla ossidazione ha limitato di molto le possibilità di indagine, fra l’altro proprio il materiale candidato alla sua sostituzione è quello più indietro nella fase di sviluppo. Per quanto riguarda gli UHTC infine, non vi sono stati particolari difficoltà: entrambi i materiali sono stati gestiti senza particolari problemi e hanno consentito di portare avanti le attività previste. Si segnala il sensibile progresso in termini di attivazione di meccanismi di protezione dall’ossidazione a caldo, specialmente alle temperature più alte sperimentate (1700 °C). Infine la fase di simulazione numerica ha consentito di condurre simulazioni termomeccaniche fortemente non lineari, sia in termini di proprietà dei materiali che di dipendenza non lineare dalla temperatura. Gli output delle simulazioni hanno consentito di indirizzare la futura fase di scelta della configurazione di TPS da realizzare, portando a scartare alcune configurazioni poco performanti. Purtroppo l’affidabilità delle simulazioni è stata ancora una volta parzialmente compromessa dal molibdeno: l’impossibilità di testarlo a più alte temperature fa sì che, durante la simulazione dell’esercizio, le sue proprietà meccaniche siano probabilmente sottostimate in termini di duttilità e capacità di plasticizzazione, portando il resto del sistema ad uno stato di sollecitazione molto intenso. Questo ha un notevole impatto sulla valutazione dello stato tensionale, anche perché è proprio lo strato metallico di molibdeno quello deputato ad attenuare le sollecitazioni all’interno del materiale