Keys in the Clouds: Auditable Multi-device Access to Cryptographic Credentials

Personal cryptographic keys are the foundation of many secure services, but storing these keys securely is a challenge, especially if they are used from multiple devices. Storing keys in a centralized location, like an Internet-accessible server, raises serious security concerns (e.g. server compromise). Hardware-based Trusted Execution Environments (TEEs) are a well-known solution for protecting sensitive data in untrusted environments, and are now becoming available on commodity server platforms. Although the idea of protecting keys using a server-side TEE is straight-forward, in this paper we validate this approach and show that it enables new desirable functionality. We describe the design, implementation, and evaluation of a TEE-based Cloud Key Store (CKS), an online service for securely generating, storing, and using personal cryptographic keys. Using remote attestation, users receive strong assurance about the behaviour of the CKS, and can authenticate themselves using passwords while avoiding typical risks of password-based authentication like password theft or phishing. In addition, this design allows users to i) define policy-based access controls for keys; ii) delegate keys to other CKS users for a specified time and/or a limited number of uses; and iii) audit all key usages via a secure audit log. We have implemented a proof of concept CKS using Intel SGX and integrated this into GnuPG on Linux and OpenKeychain on Android. Our CKS implementation performs approximately 6,000 signature operations per second on a single desktop PC. The latency is in the same order of magnitude as using locally-stored keys, and 20x faster than smart cards.Comment: Extended version of a paper to appear in the 3rd Workshop on Security, Privacy, and Identity Management in the Cloud (SECPID) 201

Anisotropic magnetoresistance and anisotropic tunneling magnetoresistance due to quantum interference in ferromagnetic metal break junctions

We measure the low-temperature resistance of permalloy break junctions as a function of contact size and the magnetic field angle, in applied fields large enough to saturate the magnetization. For both nanometer-scale metallic contacts and tunneling devices we observe large changes in resistance with angle, as large as 25% in the tunneling regime. The pattern of magnetoresistance is sensitive to changes in bias on a scale of a few mV. We interpret the effect as a consequence of conductance fluctuations due to quantum interference.Comment: 4 pages, 4 figures. Changes in response to reviewer comments. New data provide information about the mechanism causing the AMR and TAM

Analisis Sistem Antrian Dan Optimalisai Pelayanan Teller Pada PT. Bank Sulutgo

Antrian merupakan suatu garis tunggu dari nasabah (satuan) yang memerlukan layanan dari satu atau lebih pelayan (fasilitas layanan). Pada Kenyataanya, antrian diakibatkan waktu menunggu lebih lama daripada waktu pelayanan. Tujuan dari penelitian ini adalah untuk menganalisis penerapan model M/M/S pada sistem antrian Bank SulutGo cabang utama. Langkah pertama yang dilakukan adalah mengambil data kedatangan antrian nasabah. Hasil perhitungan dengan model M/M/S pada Bank SulutGo cabang utama menerapkan disiplin antrian yaitu first come first serve (FCFS). Pola kedatangan nasabah berdistribusi Poisson dan pola pelayanan berdistribusi Eksponensial. Dari hasil perhitungan rata-rata jumlah nasabah yang menunggu dalam sistem terpanjang pada periode waktu 12.00 -13.00 yaitu sebanyak 5,1353 orang atau = 5 orang. Sedangkan jumlah rata-rata nasabah yang menunggu dalam sistem terpendek terjadi pada periode waktu 08.00 – 09.00 yaitu sebanyak 0,8338 orang atau = 1 orang. Rata-rata jumlah nasabah dalam antrian terjadi pada periode waktu 12.00 – 13.00 yaitu sebanyak 1,385 orang atau = 1 orang dapat disimpulkan kinerja system antrian Bank SulutGo cabang utama optimal

Symmetric Operation of the Resonant Exchange Qubit

We operate a resonant exchange qubit in a highly symmetric triple-dot configuration using IQ-modulated RF pulses. At the resulting three-dimensional sweet spot the qubit splitting is an order of magnitude less sensitive to all relevant control voltages, compared to the conventional operating point, but we observe no significant improvement in the quality of Rabi oscillations. For weak driving this is consistent with Overhauser field fluctuations modulating the qubit splitting. For strong driving we infer that effective voltage noise modulates the coupling strength between RF drive and the qubit, thereby quickening Rabi decay. Application of CPMG dynamical decoupling sequences consisting of up to n = 32 {\pi} pulses significantly prolongs qubit coherence, leading to marginally longer dephasing times in the symmetric configuration. This is consistent with dynamical decoupling from low frequency noise, but quantitatively cannot be explained by effective gate voltage noise and Overhauser field fluctuations alone. Our results inform recent strategies for the utilization of partial sweet spots in the operation and long-distance coupling of triple-dot qubits.Comment: 6 pages, 5 figure

Negative spin exchange in a multielectron quantum dot

By operating a one-electron quantum dot (fabricated between a multielectron dot and a one-electron reference dot) as a spectroscopic probe, we study the spin properties of a gate-controlled multielectron GaAs quantum dot at the transition between odd and even occupation number. We observe that the multielectron groundstate transitions from spin-1/2-like to singlet-like to triplet-like as we increase the detuning towards the next higher charge state. The sign reversal in the inferred exchange energy persists at zero magnetic field, and the exchange strength is tunable by gate voltages and in-plane magnetic fields. Complementing spin leakage spectroscopy data, the inspection of coherent multielectron spin exchange oscillations provides further evidence for the sign reversal and, inferentially, for the importance of non-trivial multielectron spin exchange correlations.Comment: 8 pages, including 4 main figures and 2 supplementary figurure

Options for Processing Shrimp Landed in South Carolina

Resource /Energy Economics and Policy,

Noise suppression using symmetric exchange gates in spin qubits

We demonstrate a substantial improvement in the spin-exchange gate using symmetric control instead of conventional detuning in GaAs spin qubits, up to a factor-of-six increase in the quality factor of the gate. For symmetric operation, nanosecond voltage pulses are applied to the barrier that controls the interdot potential between quantum dots, modulating the exchange interaction while maintaining symmetry between the dots. Excellent agreement is found with a model that separately includes electrical and nuclear noise sources for both detuning and symmetric gating schemes. Unlike exchange control via detuning, the decoherence of symmetric exchange rotations is dominated by rotation-axis fluctuations due to nuclear field noise rather than direct exchange noise.Comment: 5 pages main text (4 figures) plus 5 pages supplemental information (3 figures

Psychopathology in children: Improvement of quality of life without psychiatric symptom reduction

Objective: The aim of this study was to assess the association between change in psychopathology and Quality of Life (QoL) across time in children with high levels of psychopathology. Methods: A referred sample of 126 seven- to 19-year-olds was studied across a 1-year follow-up period. Information concerning QoL and psychopathology was obtained from parents. Results: Overall, 38.1% of children showed neither psychiatric symptom reduction nor QoL improvement, 33.3% of children showed both a clinically significant psychiatric symptom reduction and QoL improvement, and 28.6% of children showed either psychiatric symptom reduction or QoL improvement. In 11.1% of all children,QoL improved, while the level of psychopathology remained high. Age, gender, or psychiatric diagnosis did not predict a poor outcome of persistently high psychopathology scores and poor QoL. Conclusion: QoL in children with psychiatric problems may be improved by reducing psychiatric symptoms in a number of children, but it is also possible to improve QoL without psychiatric symptom reduction. This implicates that QoL should become an important aim and treatment outcome measure of psychiatric treatment programs, especially since psychopathology tends to persist. © Steinkopff Verlag 2005