Security Analysis of End-to-End Encryption for Zoom Meetings

In the wake of the global COVID-19 pandemic, video conference systems have become essential for not only business purposes, but also private, academic, and educational uses. Among the various systems, Zoom is the most widely deployed video conference system. In October 2020, Zoom Video Communications rolled out their end-to-end encryption (E2EE) to protect conversations in a meeting from even insiders, namely, the service provider Zoom. In this study, we conduct thorough security evaluations of the E2EE of Zoom (version 2.3.1) by analyzing their cryptographic protocols. We discover several attacks more powerful than those expected by Zoom according to their whitepaper. Specifically, if insiders collude with meeting participants, they can impersonate any Zoom user in target meetings, whereas Zoom indicates that they can impersonate only the current meeting participants. Besides, even without relying on malicious participants, insiders can impersonate any Zoom user in target meetings though they cannot decrypt meeting streams. In addition, we demonstrate several impersonation attacks by meeting participants or insiders colluding with meeting participants. Although these attacks may be beyond the scope of the security claims made by Zoom or may be already mentioned in the whitepaper, we reveal the details of the attack procedures and their feasibility in the real-world setting and propose effective countermeasures in this paper. Our findings are not an immediate threat to the E2EE of Zoom; however, we believe that these security evaluations are of value for deeply understanding the security of E2EE of Zoom

Synthesis of 2-and 6-thienylazulenes by palladium-catalyzed direct arylation of 2-and 6-haloazulenes with thiophene derivatives

Preparation of 2- and 6-thienylazulene derivatives was established by the palladium-catalyzed direct cross-coupling reaction of 2- and 6-haloazulenes with the corresponding thiophene derivatives in good yield. Several thienylazulene derivatives were also used in the reaction with 2-chloroazulene derivatives in the presence of the palladium-catalyst to afford the thiophene derivatives with two azulene functions in good yield.ArticleORGANIC & BIOMOLECULAR CHEMISTRY. 23(66):10191-10197 (2015)journal articl

Security Analysis of SFrame

As people become more and more privacy conscious, the need for end-to-end encryption (E2EE) has become widely recognized. We study herein the security of SFrame, an E2EE mechanism recently proposed to the Internet Engineering Task Force for video/audio group communications over the Internet. Despite being a quite recent project, SFrame is going to be adopted by a number of real-world applications. We inspect the original specification of SFrame and find critical issues that will lead to impersonation (forgery) attacks with a practical complexity by a malicious group member. We also investigate the several publicly available SFrame implementations and confirm that this issue is present in these implementations

Synthesis of 1-azulenyl ketones by Bronsted acid mediated hydration of 1-azulenylalkynes

Preparation of 1-azulenyl ketones was achieved by metal-free hydration of 1-azulenylalkynes using trifluoroacetic acid as a Bronsted acid in good to excellent yields. The reaction was accomplished at a relatively low temperature with complete regio-selectivity and compatibility of several functional groups.ArticleRSC ADVANCES. 90(1):78303-78306 (2016)journal articl

Parallel SAT Framework to Find Clustering of Differential Characteristics and Its Applications

The most crucial but time-consuming task for differential cryptanalysis is to find a differential with a high probability. To tackle this task, we propose a new SAT-based automatic search framework to efficiently figure out a differential with the highest probability under a specified condition. As the previous SAT methods (e.g., the Sun et al’s method proposed at ToSC 2021(1)) focused on accelerating the search for an optimal single differential characteristic, these are not optimized for evaluating a clustering effect to obtain a tighter differential probability of differentials. In contrast, our framework takes advantage of a method to solve incremental SAT problems in parallel using a multi-threading technique, and consequently, it offers the following advantages compared with the previous methods: (1) speedy identification of a differential with the highest probability under the specified conditions; (2) efficient construction of the truncated differential with the highest probability from the obtained multiple differentials; and (3) applicability to a wide class of symmetric-key primitives. To demonstrate the effectiveness of our framework, we apply it to the block cipher PRINCE and the tweakable block cipher QARMA. We successfully figure out the tight differential bounds for all variants of PRINCE and QARMA within the practical time, thereby identifying the longest distinguisher for all the variants, which improves existing ones by one to four more rounds. Besides, we uncover notable differences between PRINCE and QARMA in the behavior of differential, especially for the clustering effect. We believe that our findings shed light on new structural properties of these important primitives. In the context of key recovery attacks, our framework allows us to derive the key-recovery-friendly truncated differentials for all variants of QARMA. Consequently, we report key recovery attacks based on (truncated) differential cryptanalysis on QARMA for the first time and show these key recovery attacks are competitive with existing other attacks

Pemphigus Vulgaris Confined to the Gingiva: A Case Report

Pemphigus Vulgaris (PV) is an autoimmune intraepithelial blistering disease involving the skin and mucous membranes. Oral mucosa is frequently affected in patients with PV, and oral lesions may be the first sign of the disease in majority of patients. In some patients, oral lesions may also be followed by skin involvement. Therefore, timely recognition and therapy of oral lesions is critical as it may prevent skin involvement. Early oral lesions of PV are, however, often regarded as difficult to diagnose, since the initial oral lesions may be relatively nonspecific, manifesting as superficial erosions or ulcerations, and rarely presenting with the formation of intact bullae. Lesions may occur anywhere on the oral mucosa including gingiva; however; desquamtive gingivitis is less common with PV than other mucocutaneous conditions such as pemphigoid or lichen planus. This paper describes the case of a patient presenting with a one-year history of painful gingival, who is finally diagnosed as having PV

Synthesis of 1,2 '-Biazulenes by Palladium-Catalyzed Unusual Homocoupling Reaction of 1-Haloazulenes in the Presence of Ferrocene

The synthesis of 1,2-biazulenes was established by palladium-catalyzed homocoupling reactions of the corresponding 1-haloazulenes in the presence of ferrocene. The optical properties of the novel 1,2-biazulenes were investigated by UV/Vis spectroscopy and theoretical calculations. The redox behaviors of 1,2-biazulenes were also examined by cyclic voltammetry (CV) and differential pulse voltammetry (DPV).ArticleSYNTHESIS. 89(11):2438-2448 (2016)journal articl

Influence of Ge composition in the Cu2Sn1-xGexS3 thin-film photovoltaic absorber prepared by sulfurization of laminated metallic precursor

Cu2Sn1-xGexS3 thin-film absorbers are prepared by sulfurization of laminated precursors. The crystal grain size is enhanced under higher growth temperature and/or sulfur pressure. By the XRD and Raman analyses, the crystal alloy is considered to be composed of majority monoclinic phase with minority secondary phase such as Cu-2(Sn1-xGex)(3)S-7 throughout the whole Ge/(Ge+Sn) composition range. The optical band gap is observed to be varied between 0.94 eV and 1.30 eV in relation with the Ge contents. A photovoltaic conversion efficiency of about 2% is obtained in the sample utilizing Cu2Sn0.6Ge0.4S3 absorber. (C) 2015 Elsevier B.V. All rights reserved.ArticleSOLAR ENERGY MATERIALS AND SOLAR CELLS. 140:312-319 (2015)journal articl