Halitosis in Hong Kong: a community based study

Includes bibliographical references (p. 27-29).published_or_final_versio

Attribute-based Anonymous Credential: Optimization for Single-Use and Multi-Use

User attributes can be authenticated by an attribute-based anonymous credential while keeping the anonymity of the user. Most attribute-based anonymous credential schemes are designed specifically for either multi-use or single-use. In this paper, we propose a unified attribute-based anonymous credential system, in which users always obtain the same format of credential from the issuer. The user can choose to use it for an efficient multi-use or single-use show proof. It is a more user-centric approach than the existing schemes. Technically, we propose an interactive approach to the credential issuance protocol using a two-party computation with an additive homomorphic encryption. At the same time, it keeps the security property of impersonation resilience, anonymity, and unlinkability. Apart from the interactive protocol, we further design the show proofs for efficient single-use credentials which maintain the user anonymity

DIDO: Data Provenance from Restricted TLS 1.3 Websites

Public data can be authenticated by obtaining from a trustworthy website with TLS. Private data, such as user profile, are usually restricted from public access. If a user wants to authenticate his private data (e.g., address) provided by a restricted website (e.g., user profile page of a utility company website) to a verifier, he cannot simply give his username and password to the verifier. DECO (CCS 2020) provides a solution for liberating these data without introducing undesirable trust assumption, nor requiring server-side modification. Their implementation is mainly based on TLS 1.2. In this paper, we propose an optimized solution for TLS 1.3 websites. We tackle a number of open problems, including the support of X25519 key exchange in TLS 1.3, the design of round-optimal three-party key exchange, the architecture of two-party computation of TLS 1.3 key scheduling, and circuit design optimized for two-party computation. We test our implementation with real world website and show that our optimization is necessary to avoid timeout in TLS handshake

Efficient Multiplicative-to-Additive Function from Joye-Libert Cryptosystem and Its Application to Threshold ECDSA

Threshold ECDSA receives interest lately due to its widespread adoption in blockchain applications. A common building block of all leading constructions involves a secure conversion of multiplicative shares into additive ones, which is called the multiplicative-to-additive (MtA) function. MtA dominates the overall complexity of all existing threshold ECDSA constructions. Specifically, $O(n^2)$ invocations of MtA are required in the case of $n$ active signers. Hence, improvement of MtA leads directly to significant improvements for all state-of-the-art threshold ECDSA schemes. In this paper, we design a novel MtA by revisiting the Joye-Libert (JL) cryptosystem. Specifically, we revisit JL encryption and propose a JL-based commitment, then give efficient zero-knowledge proofs for JL cryptosystem which are the first to have standard soundness. Our new MtA offers the best time-space complexity trade-off among all existing MtA constructions. It outperforms state-of-the-art constructions from Paillier by a factor of $1.85$ to $2$ in bandwidth and $1.2$ to $1.7$ in computation. It is $7\times$ faster than those based on Castagnos-Laguillaumie encryption only at the cost of $2\times$ more bandwidth. While our MtA is slower than OT-based constructions, it saves $18.7\times$ in bandwidth requirement. In addition, we also design a batch version of MtA to further reduce the amotised time and space cost by another $25$%

Clinical and neuroradiological features of viral encephalitis: a hospital-based study

Oral PresentationThis journal supplement contains abstracts from the 17th MRC; Dept. of Medicine, The University of Hong Kong, Queen Mary Hospital, Hong KongTopics: Basic science, translational and clinical researchINTRODUCTION: Viral encephalitis is an important infection of the central nervous system with significant morbidity and mortality. We studied the clinical, laboratory and radiological characteristics of viral encephalitis patients managed in our hospital, focusing on factors associated with poor prognosis. METHODS: We retrospectively studied the clinical features of patients diagnosed …published_or_final_versionThe 17th Medical Research Conference (MRC), Department of Medicine, University of Hong Kong, Hong Kong, 14 January 2012. In Hong Kong Medical Journal, 2012, v. 18 suppl. 1, p. 31, abstract no. 3

The fractional amplitude of low-frequency fluctuations signals related to amyloid uptake in high-risk populations—A pilot fMRI study

BackgroundPatients with type 2 diabetes mellitus (T2DM) and subjective cognitive decline (SCD) have a higher risk to develop Alzheimer's Disease (AD). Resting-state-functional magnetic resonance imaging (rs-fMRI) was used to document neurological involvement in the two groups from the aspect of brain dysfunction. Accumulation of amyloid-β (Aβ) starts decades ago before the onset of clinical symptoms and may already have been associated with brain function in high-risk populations. However, this study aims to compare the patterns of fractional amplitude of low-frequency fluctuations (fALFF) maps between cognitively normal high-risk groups (SCD and T2DM) and healthy elderly and evaluate the association between regional amyloid deposition and local fALFF signals in certain cortical regions.Materials and methodsA total of 18 T2DM, 11 SCD, and 18 healthy elderlies were included in this study. The differences in the fALFF maps were compared between HC and high-risk groups. Regional amyloid deposition and local fALFF signals were obtained and further correlated in two high-risk groups.ResultsCompared to HC, the altered fALFF signals of regions were shown in SCD such as the left posterior cerebellum, left putamen, and cingulate gyrus. The T2DM group illustrated altered neural activity in the superior temporal gyrus, supplementary motor area, and precentral gyrus. The correlation between fALFF signals and amyloid deposition was negative in the left anterior cingulate cortex for both groups. In the T2DM group, a positive correlation was shown in the right occipital lobe and left mesial temporal lobe.ConclusionThe altered fALFF signals were demonstrated in high-risk groups compared to HC. Very early amyloid deposition in SCD and T2DM groups was observed to affect the neural activity mainly involved in the default mode network (DMN)

Spatial analysis of the impact of urban geometry and socio-demographic characteristics on COVID-19, a study in Hong Kong

The World Health Organization considered the widespread of COVID-19 over the world as a pandemic. There is still a lack of understanding of its origin, transmission, and treatment methods. Understanding the influencing factors of the COVID-19 can help mitigate its spread, but little research on the spatial factors has been conducted. Therefore, this study explores the effects of urban geometry and socio-demographic factors on the COVID-19 cases in Hong Kong. For each patient, the places they visited during the incubation period before going to hospital were identified, and matched with corresponding attributes of urban geometry (i.e., building geometry, road network, greenspace) and socio-demographic factors (i.e., demographic, educational, economic, household and housing characteristics) based on the coordinates. The local cases were then compared with the imported cases using the stepwise logistic regression, the logistic regression with case-control of time, and the least absolute shrinkage and selection operator regression to identify factors influencing local disease transmission. Results show that the building geometry, road network and certain socio-economic characteristics are significantly associated with COVID-19 cases. In addition, the results indicate that urban geometry is playing a more important role than the socio-demographic characteristics in affecting the COVID-19 incidences. These findings provide a useful reference to the government and the general public as to the spatial vulnerability of the COVID-19 transmission and to take appropriate preventive measures in high-risk areas

Phylodynamics of HIV-1 Subtype B among the Men-Having-Sex-with-Men (MSM) Population in Hong Kong

The men-having-sex-with-men (MSM) population has become one of the major risk groups for HIV-1 infection in the Asia Pacific countries. Hong Kong is located in the centre of Asia and the transmission history of HIV-1 subtype B transmission among MSM remained unclear. The aim of this study was to investigate the transmission dynamics of HIV-1 subtype B virus in the Hong Kong MSM population. Samples of 125 HIV-1 subtype B infected MSM patients were recruited in this study. Through this study, the subtype B epidemic in the Hong Kong MSM population was identified spreading mainly among local Chinese who caught infection locally. On the other hand, HIV-1 subtype B infected Caucasian MSM caught infection mainly outside Hong Kong. The Bayesian phylogenetic analysis also indicated that 3 separate subtype B epidemics with divergence dates in the 1990s had occurred. The first and latest epidemics were comparatively small-scaled; spreading among the local Chinese MSM while sauna-visiting was found to be the major sex partner sourcing reservoir for the first subtype B epidemic. However, the second epidemic was spread in a large-scale among local Chinese MSM with a number of them having sourced their sex partners through the internet. The epidemic virus was estimated to have a divergence date in 1987 and the infected population in Hong Kong had a logistic growth throughout the past 20 years. Our study elucidated the evolutionary and demographic history of HIV-1 subtype B virus in Hong Kong MSM population. The understanding of transmission and growth model of the subtype B epidemic provides more information on the HIV-1 transmission among MSM population in other Asia Pacific high-income countries

Increased Genetic Diversity of HIV-1 Circulating in Hong Kong

HIV-1 group M strains are characterized into 9 pure subtypes and 48 circulating recombinant forms (CRFs). Recent studies have identified the presence of new HIV-1 recombinants in Hong Kong and their complexity continues to increase. This study aims to characterize the HIV-1 genetic diversity in Hong Kong. Phylogenetic analyses were performed by using HIV-1 pol sequences including protease and partial reverse transcriptase isolated from 1045 local patients in Hong Kong from 2003 to 2008. For the pol sequences with unassigned genotype, the evidence of recombination was determined by using sliding-window based bootscan plots and their env C2V3 region were also sequenced. Epidemiological background of these patients was further collected. The pol phylogenetic analyses highlighted the extent of HIV-1 genetic diversity in Hong Kong. Subtype B (450/1045; 43.1%) and CRF01_AE (469/1045; 44.9%) variants were clearly predominant. Other genotypes (126/1045; 12.1%) including 3 defined subtypes, 10 CRFs, 1 unassigned subtype and 33 recombinants with 11 different mosaic patterns were observed. Recombinants of subtype B and CRF01_AE were mainly found among local Chinese MSM throughout 2004 to 2008, while the CRF02_AG and subtype G recombinants were circulating among non-Chinese Asian population in Hong Kong through heterosexual transmission starting from 2008. Our study demonstrated the complex recombination of HIV-1 in Hong Kong and the need in developing surveillance system for tracking the distribution of new HIV-1 genetic variants