PA-Boot: A Formally Verified Authentication Protocol for Multiprocessor Secure Boot

Hardware supply-chain attacks are raising significant security threats to the boot process of multiprocessor systems. This paper identifies a new, prevalent hardware supply-chain attack surface that can bypass multiprocessor secure boot due to the absence of processor-authentication mechanisms. To defend against such attacks, we present PA-Boot, the first formally verified processor-authentication protocol for secure boot in multiprocessor systems. PA-Boot is proved functionally correct and is guaranteed to detect multiple adversarial behaviors, e.g., processor replacements, man-in-the-middle attacks, and tampering with certificates. The fine-grained formalization of PA-Boot and its fully mechanized security proofs are carried out in the Isabelle/HOL theorem prover with 306 lemmas/theorems and ~7,100 LoC. Experiments on a proof-of-concept implementation indicate that PA-Boot can effectively identify boot-process attacks with a considerably minor overhead and thereby improve the security of multiprocessor systems.Comment: Manuscript submitted to IEEE Trans. Dependable Secure Compu

Empirical Review of Smart Contract and DeFi Security: Vulnerability Detection and Automated Repair

Decentralized Finance (DeFi) is emerging as a peer-to-peer financial ecosystem, enabling participants to trade products on a permissionless blockchain. Built on blockchain and smart contracts, the DeFi ecosystem has experienced explosive growth in recent years. Unfortunately, smart contracts hold a massive amount of value, making them an attractive target for attacks. So far, attacks against smart contracts and DeFi protocols have resulted in billions of dollars in financial losses, severely threatening the security of the entire DeFi ecosystem. Researchers have proposed various security tools for smart contracts and DeFi protocols as countermeasures. However, a comprehensive investigation of these efforts is still lacking, leaving a crucial gap in our understanding of how to enhance the security posture of the smart contract and DeFi landscape. To fill the gap, this paper reviews the progress made in the field of smart contract and DeFi security from the perspective of both vulnerability detection and automated repair. First, we analyze the DeFi smart contract security issues and challenges. Specifically, we lucubrate various DeFi attack incidents and summarize the attacks into six categories. Then, we present an empirical study of 42 state-of-the-art techniques that can detect smart contract and DeFi vulnerabilities. In particular, we evaluate the effectiveness of traditional smart contract bug detection tools in analyzing complex DeFi protocols. Additionally, we investigate 8 existing automated repair tools for smart contracts and DeFi protocols, providing insight into their advantages and disadvantages. To make this work useful for as wide of an audience as possible, we also identify several open issues and challenges in the DeFi ecosystem that should be addressed in the future.Comment: This paper is submitted to the journal of Expert Systems with Applications (ESWA) for revie

Hydroxyl super rotors from vacuum ultraviolet photodissociation of water

Free electron lasers provide a state-of-the-art tool to investigate the photochemistry of water. Here, the authors show that highly rotationally excited hydroxyl radicals, so-called “super rotors” existing above the bond dissociation energy, are observed from the photodissociation of water, which may have implications for understanding the interstellar medium

Rapid biological nanoparticles assay through immunomagnetic extraction and nanophotonic label-free detection

Exosomes have been considered as high-quality biomarkers for disease diagnosis, as they are secreted by cells into extracellular environments as nanovesicles with rich and unique molecular information, and can be isolated and enriched from clinical samples. However, most existing exosome assays, to date, require time-consuming isolation and purification procedures; the detection specificity and sensitivity are also in need of improvement for the realization of exosome-based disease diagnostics. This paper reports a unique all-in-one exosome assay technology that enables completing both magnetic nanoparticle (MNP)-based exosome extraction and high-sensitivity photonic crystal (PC)-based label-free exosome detection in a single miniature vessel within one hour, while providing an improved sensitivity and selectivity. High specificity of the assay to membrane antigens is realized by functionalizing both the MNPs and the PC with specific antibodies. A low limit of detection on the order of 107 exosome particles per milliliter (volume) is achieved because the conjugated MNP-exosomes nanocomplexes offer a larger index change on the PC surface, compared to the exosomes alone without using MNPs. Briefly, the all-in-one exosome assay involves (i) forming specific MNP-exosomes nanocomplexes to enrich exosomes from complex samples directly on the PC surface at the bottom of the vessel, with a >500 enrichment factor, and (ii) subsequently, performing in-situ quantification of the nanocomplexes using the PC biosensor. The present exosome assay method is validated in analyzing multiple membrane proteins of the exosomes derived from murine macrophage cells with high selectivity and sensitivity, while requiring only about one hour. This all-in-one assay technology will provide a great potential for exosome-based disease diagnostics

A Study on the Combustion Performance of Diesel Engines with O2 and CO2 Suction

Based on the chemical reaction mechanism of fuel combustion, NOx in the diesel emissions is mainly generated from N2 inside the burning environment of engine cylinder. Taking the gas mixture, O2 and CO2, as the intake air, nitrogen-free intake is accessible, and through simulative calculations and experiments, researchers can make a study of the ignition and combustion performances of the engines. Taking a type of “4135ACa” diesel engine as the research object, the study suggested the following: in the environment of O2 and CO2, only when the volume fraction of O2 reaches 45% can the engine be ignited and kept running; engine operation became more steady after its O2 percentage increased to 50%. There is no NOx emission of engine’s nitrogen-free combustion, despite some black particles in the exhaust gas. So, the bottleneck of “NOx-Soot” emission is successfully transformed into how to optimize the combustion performance of engines. Additionally, through simulative calculations, influences of the O2 volume fraction on the nitrogen-free combustion performance have been researched; results suggested that it can help promote the burning efficiency with the increase of O2. When it reached 60%, its heat output in the cylinder has been equal to that under the operation condition of air intake. Therefore, nitrogen-free combustion can be used in some NOx control area, especially to some power plant which worked underwater. The huge gas consumption can be recycled from exhaust gas by closed cycle

Analysis of Postoperative Reoperation for Congenital Duodenal Obstruction

To analyse the risk factors for reoperation after initial surgical repair of congenital duodenal obstruction and demonstrate that they can be decreased with more careful attention and more advanced techniques during surgery. Methods: The records of newborns and infants (aged 0-2 months) who had surgical therapy for congenital duodenal obstruction in the past 30 years were reviewed and analysed. Of the 298 patients, 132 (44%) were boys and 166 (56%) were girls. All patients who underwent repeat surgery postoperatively were evaluated by the reasons for surgery. The number of patients with various combination lesions of congenital duodenal obstruction was also calculated and the relationship to postoperative reoperation was analysed. Results: Twenty patients (6.7%) had congenital duodenal obstruction with combination lesions including duodenal web, malrotation, annular pancreas and multiple duodenal web. Twelve patients required further operation 5 days to 2 years postoperatively for complications (n = 5) and other duodenal atresias that were not discovered initially (n = 7). Conclusion: More than half of reoperated patients (7/12) had multiple lesions of duodenal obstruction that were missed during the primary operation. The postoperative reoperation rate for congenital duodenal obstruction could be decreased with more careful attention to operative details and more preoperative and intraoperative evaluation of the gastrointestinal tract

Diagnostic Scoring System of Hirschsprung's Disease in the Neonatal Period

Eighty to ninety percent of Hirschsprung's disease (HD) patients present in newborns. However, the diagnosis of HD in the neonatal period remains difficult. Our present study aims to propose a diagnostic scoring system and hope this will increase early diagnosis of HD and avoid unnecessary rectal biopsy. Methods: In the first study period, 57 suspected HD patients (0-3 months) completed our predetermined study protocol in which barium enema (BE), rectal manometry (RM) and full-thickness rectal biopsy were performed. Symptoms, signs and investigations were analysed for their correlation with HD diagnosis. A HD diagnostic scoring system was developed according to the statistical results and was assessed in 74 patients in the second study period. Results: Forty-five patients were diagnosed with HD in the first study period. A HD scoring system was developed in which delayed meconium, tight anus, BE and RM were diagnostic factors. A cut-off point of 3 provided 84% of HD patients score > 3, whereas 75% non-HD patients score £ 3 (p < 0.05). In the second study group, patients with score £ 3 were selected for rectal biopsy. Conclusion: In the neonatal period, using a HD scoring system may help to select patients for further invasive investigation so that unnecessary biopsy can be avoided