Open-TEE - An Open Virtual Trusted Execution Environment

Hardware-based Trusted Execution Environments (TEEs) are widely deployed in mobile devices. Yet their use has been limited primarily to applications developed by the device vendors. Recent standardization of TEE interfaces by GlobalPlatform (GP) promises to partially address this problem by enabling GP-compliant trusted applications to run on TEEs from different vendors. Nevertheless ordinary developers wishing to develop trusted applications face significant challenges. Access to hardware TEE interfaces are difficult to obtain without support from vendors. Tools and software needed to develop and debug trusted applications may be expensive or non-existent. In this paper, we describe Open-TEE, a virtual, hardware-independent TEE implemented in software. Open-TEE conforms to GP specifications. It allows developers to develop and debug trusted applications with the same tools they use for developing software in general. Once a trusted application is fully debugged, it can be compiled for any actual hardware TEE. Through performance measurements and a user study we demonstrate that Open-TEE is efficient and easy to use. We have made Open- TEE freely available as open source.Comment: Author's version of article to appear in 14th IEEE International Conference on Trust, Security and Privacy in Computing and Communications, TrustCom 2015, Helsinki, Finland, August 20-22, 201

On Making Emerging Trusted Execution Environments Accessible to Developers

New types of Trusted Execution Environment (TEE) architectures like TrustLite and Intel Software Guard Extensions (SGX) are emerging. They bring new features that can lead to innovative security and privacy solutions. But each new TEE environment comes with its own set of interfaces and programming paradigms, thus raising the barrier for entry for developers who want to make use of these TEEs. In this paper, we motivate the need for realizing standard TEE interfaces on such emerging TEE architectures and show that this exercise is not straightforward. We report on our on-going work in mapping GlobalPlatform standard interfaces to TrustLite and SGX.Comment: Author's version of article to appear in 8th Internation Conference of Trust & Trustworthy Computing, TRUST 2015, Heraklion, Crete, Greece, August 24-26, 201

Topological entanglement entropy in Gutzwiller projected spin liquids

The topological entanglement entropy(TEE) of Gutzwiller projected RVB state is studied with Monte Carlo simulation. New tricks are proposed to improve the convergence of TEE, which enable us to show that the spin liquid state studied in Ref.\cite{Vishwanath} actually does not support $Z_{2}$ topological order, a conclusion that is consistent with the information drawn from the inspection of the topological degeneracy on the same state. We find both a long ranged RVB amplitude and an approximate Marshall sign structure are at the origin of the suppression of vison gap in this spin liquid state. On the other hand, robust signature of $Z_{2}$ topological order, i.e., a TEE of $\ln2$, is clearly demonstrated for a Gutzwiiler projected RVB state on triangular lattice which is evolved from the RVB state proposed originally by Anderson\cite{Sorella}. We also find that it is the sign, rather than the amplitude of the RVB wave function, that dominates the TEE and is responsible for a positive value of TEE, which implies that the nonlocal entanglement in the RVB state is mainly encoded in the sign of the RVB wave function. Our results indicate that some information that is important for the topological property of a RVB state is missed in the effective field theory description and that a $Z_{2}$ gauge structure in the saddle point action is not enough for the RVB state to exhibit topological order, even if its spin correlation is extremely short ranged.Comment: 9 page

Entanglement Entropy of Gapped Phases and Topological Order in Three dimensions

We discuss entanglement entropy of gapped ground states in different dimensions, obtained on partitioning space into two regions. For trivial phases without topological order, we argue that the entanglement entropy may be obtained by integrating an `entropy density' over the partition boundary that admits a gradient expansion in the curvature of the boundary. This constrains the expansion of entanglement entropy as a function of system size, and points to an even-odd dependence on dimensionality. For example, in contrast to the familiar result in two dimensions, a size independent constant contribution to the entanglement entropy can appear for trivial phases in any odd spatial dimension. We then discuss phases with topological entanglement entropy (TEE) that cannot be obtained by adding local contributions. We find that in three dimensions there is just one type of TEE, as in two dimensions, that depends linearly on the number of connected components of the boundary (the `zeroth Betti number'). In D > 3 dimensions, new types of TEE appear which depend on the higher Betti numbers of the boundary manifold. We construct generalized toric code models that exhibit these TEEs and discuss ways to extract TEE in D >=3.Comment: 16.5 pages, 10 figure

Quasi-particle Statistics and Braiding from Ground State Entanglement

Topologically ordered phases are gapped states, defined by the properties of excitations when taken around one another. Here we demonstrate a method to extract the statistics and braiding of excitations, given just the set of ground-state wave functions on a torus. This is achieved by studying the Topological Entanglement Entropy (TEE) on partitioning the torus into two cylinders. In this setting, general considerations dictate that the TEE generally differs from that in trivial partitions and depends on the chosen ground state. Central to our scheme is the identification of ground states with minimum entanglement entropy, which reflect the quasi-particle excitations of the topological phase. The transformation of these states allows for a determination of the modular S and U matrices which encode quasi-particle properties. We demonstrate our method by extracting the modular S matrix of an SU(2) spin symmetric chiral spin liquid phase using a Monte Carlo scheme to calculate TEE, and prove that the quasi-particles obey semionic statistics. This method offers a route to a nearly complete determination of the topological order in certain cases.Comment: revised for clarity; 17 pages, 9 figures, 1 tabl

Temperature-sensed cryogenic bleed maintains liquid state in transfer line

Inverted tee, installed at a high point in a cryogenic transfer line, is equipped with an insulated bleed line that passes a fixed amount of cryogenic fluid at atmospheric pressure. A sensing device activates a vent valve in the tee stack whenever gaseous nitrogen is present