15 research outputs found
Assessing the Privacy Benefits of Domain Name Encryption
As Internet users have become more savvy about the potential for their
Internet communication to be observed, the use of network traffic encryption
technologies (e.g., HTTPS/TLS) is on the rise. However, even when encryption is
enabled, users leak information about the domains they visit via DNS queries
and via the Server Name Indication (SNI) extension of TLS. Two recent proposals
to ameliorate this issue are DNS over HTTPS/TLS (DoH/DoT) and Encrypted SNI
(ESNI). In this paper we aim to assess the privacy benefits of these proposals
by considering the relationship between hostnames and IP addresses, the latter
of which are still exposed. We perform DNS queries from nine vantage points
around the globe to characterize this relationship. We quantify the privacy
gain offered by ESNI for different hosting and CDN providers using two
different metrics, the k-anonymity degree due to co-hosting and the dynamics of
IP address changes. We find that 20% of the domains studied will not gain any
privacy benefit since they have a one-to-one mapping between their hostname and
IP address. On the other hand, 30% will gain a significant privacy benefit with
a k value greater than 100, since these domains are co-hosted with more than
100 other domains. Domains whose visitors' privacy will meaningfully improve
are far less popular, while for popular domains the benefit is not significant.
Analyzing the dynamics of IP addresses of long-lived domains, we find that only
7.7% of them change their hosting IP addresses on a daily basis. We conclude by
discussing potential approaches for website owners and hosting/CDN providers
for maximizing the privacy benefits of ESNI.Comment: In Proceedings of the 15th ACM Asia Conference on Computer and
Communications Security (ASIA CCS '20), October 5-9, 2020, Taipei, Taiwa
Experimental investigation of particle contact laws for discrete element model of granular materials
Pressure-assisted sintering of high purity barium titanate
The dielectric behaviour of High Purity Barium titanate (HPB) ceramics is strongly dependent on the grain size and porosity. For applications, control of grain size and porosity is required. Pressure-assisted sintering techniques at relatively low temperatures meet these requirements. In this study, hot-pressing (without a die) in the temperature range 1050°C-1200°C was investigated, using stacks of tape casted HPB foils with a typical grain size of 1.2 µm. The samples were pressed up to 60 minutes, applying a uniaxial pressure between 1 and 75 MPa. No lower threshold pressure for densification was observed in the pressure range studied and the lowest temperature to reach full density was determined to equal 1100°C. Using the experimental densification data, the applicability of the densification model as reported by Besson and Abouaf [1] was studied. Experimental process control was found to be possible, but this control remains empirical since the studied model was not capable of describing the actual physical situation properly
Thermal and mechanical properties of modified CaCO3 filled poly (ethylene terephthalate) nanocomposites
Poly(ethylene terephthalate) (PET)/CaCO3 and PET/modified-CaCO3 (m-CaCO3) nanocomposites were prepared by melt blending. The morphology indicated that m-CaCO3 produced by reacting sodium oxalate and calcium chloride, was well dispersed in PET matrix and showed good interfacial interaction with PET compared to CaCO3. No significant differences in the thermal properties such as, glass transition, melting and degradation temperatures, of the nanocomposites were observed. The thermal shrinkage of PET at 120 ??C was 10.8 %, while those of PET/CaCO3 and PET/m-CaCO3 nanocomposites were 2.9-5.2 % and 1.2-2.8 %, respectively depending on filler content. The tensile strength of PET/CaCO3 nanocomposite decreased with CaCO3 loading, whereas that of PET/m-CaCO3 nanocomposites at 0.5 wt% loading showed a 17 % improvement as compared to neat PET. The storage modulus at 120 ??C increased from 1660 MPa for PET to 2350 MPa for PET/CaCO3 nanocomposite at 3 wt% loading, and 3230 MPa for PET/m-CaCO3 nanocomposite at 1 wt% loadinclose0