Evading Classifiers by Morphing in the Dark

Learning-based systems have been shown to be vulnerable to evasion through adversarial data manipulation. These attacks have been studied under assumptions that the adversary has certain knowledge of either the target model internals, its training dataset or at least classification scores it assigns to input samples. In this paper, we investigate a much more constrained and realistic attack scenario wherein the target classifier is minimally exposed to the adversary, revealing on its final classification decision (e.g., reject or accept an input sample). Moreover, the adversary can only manipulate malicious samples using a blackbox morpher. That is, the adversary has to evade the target classifier by morphing malicious samples "in the dark". We present a scoring mechanism that can assign a real-value score which reflects evasion progress to each sample based on the limited information available. Leveraging on such scoring mechanism, we propose an evasion method -- EvadeHC -- and evaluate it against two PDF malware detectors, namely PDFRate and Hidost. The experimental evaluation demonstrates that the proposed evasion attacks are effective, attaining $100\%$ evasion rate on the evaluation dataset. Interestingly, EvadeHC outperforms the known classifier evasion technique that operates based on classification scores output by the classifiers. Although our evaluations are conducted on PDF malware classifier, the proposed approaches are domain-agnostic and is of wider application to other learning-based systems

EFFECTS OF SOURCE DOPING PROFILE ON DEVICE CHARACTERISTICS OF LATERAL AND VERTICAL TUNNEL FIELD-EFFECT TRANSISTORS

The source doping engineering, the low bandgap material and the vertical tunneling structure have recently been considered as most effective techniques to resolve the on-current issue in tunnel field-effect transistors (TFETs). In this paper, the effects of source doping profile, including the concentration and gradient, on the device characteristics are adequately elucidated in lateral and vertical TFETs using low bandgap germanium to allow a comprehensive comparison between the two major TFET architectures for the first time. Similar dependences of the on-current on the source concentration are observed in lateral and vertical TFETs, except that the on-current of vertical TFETs is always greater than that of lateral TFETs approximately one order of magnitude. With different contributions of the lateral and vertical tunneling components in the subthreshold region, the subthreshold swing of vertical TFETs first decreases at small concentrations, then increases at medium values, and finally decreases again at high concentrations, whereas that of lateral counterparts always decreases exponentially with increase in the source concentration. The on-current of lateral TFETs is significantly decreased, while that of vertical TFETs is almost invariable with increasing the source doping gradient. With competitive advantages of the vertical TFET architecture in on-current, subthreshold swing and device fabrication, vertical TFETs using low bandgap semiconductors are promising for use in low power applications

Neutron transition strengths of 21+2^+_1 states in the neutron rich Oxygen isotopes determined from inelastic proton scattering

A coupled-channel analysis of the $^{18,20,22}$O$(p,p')$ data has been performed to determine the neutron transition strengths of 2$^+_1$ states in Oxygen targets, using the microscopic optical potential and inelastic form factor calculated in the folding model. A complex density- and \emph{isospin} dependent version of the CDM3Y6 interaction was constructed, based on the Brueckner-Hatree-Fock calculation of nuclear matter, for the folding model input. Given an accurate isovector density dependence of the CDM3Y6 interaction, the isoscalar ($\delta_0$) and isovector ($\delta_1$) deformation lengths of 2$^+_1$ states in $^{18,20,22}$O have been extracted from the folding model analysis of the $(p,p')$ data. A specific $N$-dependence of $\delta_0$ and $\delta_1$ has been established which can be linked to the neutron shell closure occurring at $N$ approaching 16. The strongest isovector deformation was found for 2$^+_1$ state in $^{20}$O, with $\delta_1$ about 2.5 times larger than $\delta_0$, which indicates a strong core polarization by the valence neutrons in $^{20}$O. The ratios of the neutron/proton transition matrix elements ($M_n/M_p$) determined for 2$^+_1$ states in $^{18,20}$O have been compared to those deduced from the mirror symmetry, using the measured $B(E2)$ values of 2$^+_1$ states in the proton rich $^{18}$Ne and $^{20}$Mg nuclei, to discuss the isospin impurity in the $2^+_1$ excitation of the $A=18,T=1$ and $A=20,T=2$ isobars.Comment: Version accepted for publication in Physical Review

Mixed Fault Tolerance Protocols with Trusted Execution Environment

Blockchain systems are designed, built and operated in the presence of failures. There are two dominant failure models, namely crash fault and Byzantine fault. Byzantine fault tolerance (BFT) protocols offer stronger security guarantees, and thus are widely used in blockchain systems. However, their security guarantees come at a dear cost to their performance and scalability. Several works have improved BFT protocols, and Trusted Execution Environment (TEE) has been shown to be an effective solution. However, existing such works typically assume that each participating node is equipped with TEE. For blockchain systems wherein participants typically have different hardware configurations, i.e., some nodes feature TEE while others do not, existing TEE-based BFT protocols are not applicable. This work studies the setting wherein not all participating nodes feature TEE, under which we propose a new fault model called mixed fault. We explore a new approach to designing efficient distributed fault-tolerant protocols under the mixed fault model. In general, mixed fault tolerance (MFT) protocols assume a network of $n$ nodes, among which up to $f = \frac{n-2}{3}$ can be subject to mixed faults. We identify two key principles for designing efficient MFT protocols, namely, (i) prioritizing non-equivocating nodes in leading the protocol, and (ii) advocating the use of public-key cryptographic primitives that allow authenticated messages to be aggregated. We showcase these design principles by prescribing an MFT protocol, namely MRaft. We implemented a prototype of MRaft using Intel SGX, integrated it into the CCF blockchain framework, conducted experiments, and showed that MFT protocols can obtain the same security guarantees as their BFT counterparts while still providing better performance (both transaction throughput and latency) and scalability.Comment: 12 pages, 3 figure

Interaction between triphenylphosphine or 1,2-bis(diphenylphosphino)ethane with some complexes K[PtCl3(olefin)] (olefin: methyleugenol, safrole, isopropyl eugenoxyacetate)

Novel study on the interaction between K[PtCl3(olefin)] (olefin: methyleugenol, safrole and isopropyl eugenoxyacetate) with TPP and DPPE shows that TPP and DPPE readily replace the olefins to form complexes [PtCl2(TPP)2] (P4), [PtCl2(DPPE)] (P5) and [Pt(DPPE)2]Cl2 (P6). P4 possesses trans configuration when the molar ratio of the mono olefin and TPP of 1:1. When the ratio is 1:2, P4 is a mixture of trans and cis isomers of which trans one is prevailing. The cis isomer trends to convert to trans one in chloroform solvent. P5 and P6 were formed when the molar ratio of mono isopropyl eugenoxyacetate and DPPE of 1:1 and 1:2, respectively. The structures of P4÷P6 were elucidated by Pt analysis, ESI-MS, IR and 1H NMR spectra studies. Keywords. Pt(II) complexes, olefins, phosphine derivatives