Improved Black-Box Constructions of Composable Secure Computation

We close the gap between black-box and non-black-box constructions of $\mathit{composable}$ secure multiparty computation in the plain model under the $\mathit{minimal}$ assumption of semi-honest oblivious transfer. The notion of protocol composition we target is $\mathit{angel\text{-}based}$ security, or more precisely, security with super-polynomial helpers. In this notion, both the simulator and the adversary are given access to an oracle called an $\mathit{angel}$ that can perform some predefined super-polynomial time task. Angel-based security maintains the attractive properties of the universal composition framework while providing meaningful security guarantees in complex environments without having to trust anyone. Angel-based security can be achieved using non-black-box constructions in $\max(R_{\mathsf{OT}},\widetilde{O}(\log n))$ rounds where $R_{\mathsf{OT}}$ is the round-complexity of the semi-honest oblivious transfer. However, currently, the best known $\mathit{black\text{-}box}$ constructions under the same assumption require $\max(R_{\mathsf{OT}},\widetilde{O}(\log^2 n))$ rounds. If $R_{\mathsf{OT}}$ is a constant, the gap between non-black-box and black-box constructions can be a multiplicative factor $\log n$. We close this gap by presenting a $\max(R_{\mathsf{OT}},\widetilde{O}(\log n))$-round black-box construction. We achieve this result by constructing constant-round 1-1 CCA-secure commitments assuming only black-box access to one-way functions

Building Unclonable Cryptography: A Tale of Two No-cloning Paradigms

Unclonable cryptography builds primitives that enjoy some form of unclonability, such as quantum money, software copy protection, and bounded execution programs. These are impossible in the classical model as classical data is inherently clonable. Quantum computing, with its no-cloning principle, offers a solution. However, it is not enough to realize bounded execution programs; these require one-time memory devices that self-destruct after a single data retrieval query. Very recently, a new no-cloning technology has been introduced [Eurocrypt\u2722], showing that unclonable polymers---proteins---can be used to build bounded-query memory devices and unclonable cryptographic applications. In this paper, we investigate the relation between these two technologies; whether one can replace the other, or complement each other such that combining them brings the best of both worlds. Towards this goal, we review the quantum and unclonable polymer models, and existing unclonable cryptographic primitives. Then, we discuss whether these primitives can be built using the other technology, and show alternative constructions and notions when possible. We also offer insights and remarks for the road ahead. We believe that this study will contribute in advancing the field of unclonable cryptography on two fronts: developing new primitives, and realizing existing ones using new constructions

Improving Biomanufacturing Production with Tunable Transcriptional Regulation via Elastin-like Polypeptides

The metabolism of E. coli and other microbes can be engineered to create valuable chemicals such as biofuels, medicines, etc. However, process efficiency is limited by the toxicity of intermediates in the production pathway, which induces cellular stress and killing the production in cells. By fusing elastin-like polypeptides (ELPs) with sigma factors (SF), we propose a stress feedback system can be created to recognize cues of cellular health and autoregulate expression of bioproduction pathways for improved health and production. ELPs undergo a sharp, reversible, phase transition causing an aggregation above a certain temperature (Tt) based on conditions that align with intracellular health such as intracellular pH. This behavior, along with the ability to control Tt through sequence alterations, makes ELPs ideal sensors for controlling gene expression. Fused SF, which activated gene expression, are sequestered in ELP-SF aggregates above the transition temperature, reducing their free concentration. To evaluate the potential of ELP-SF to control gene expression, we expressed green fluorescent protein (GFP) from a promoter driven by the fused SF. In vivo, this system activated the expression of GFP at levels comparable to a SF control. However, at elevated temperatures, the system reduces gene expression by 20% relative to the control demonstrating the ability of the construct to control gene expression. The dynamic performance of the system was also modeled in MATLAB to reveal key parameters that affect system behavior. These results validate our main hypothesis and suggest a new strategy to optimize the sustainable production of valuable chemicals from microbes

Weak coupling interactions of colloidal lead sulphide nanocrystals with silicon photonic crystal nanocavities near 1.55 microns at room temperature

We observe the weak coupling of lead sulphide nanocrystals to localized defect modes of 2-dimensional silicon nanocavities. Cavity resonances characterized with ensemble nanocrystals are verified with cold-cavity measurements using integrated waveguides. Polarization dependence of the cavity field modes is observed. The linewidths measured in coupling experiments are broadened in comparison to the cold-cavity characterization, partly due to large homogeneous linewidths of the nanocrystals. The calculated Purcell factor for a single exciton is 75, showing promise toward applications in single photon systems. These novel light sources operate near 1.55 micron wavelengths at room temperature, permitting integration with current fiber communications networks.Comment: 11 pages, 4 figures, Content Modified from original manuscript with additional measurements and simulation

IST Austria Technical Report

We present an algorithmic method for the synthesis of concurrent programs that are optimal with respect to quantitative performance measures. The input consists of a sequential sketch, that is, a program that does not contain synchronization constructs, and of a parametric performance model that assigns costs to actions such as locking, context switching, and idling. The quantitative synthesis problem is to automatically introduce synchronization constructs into the sequential sketch so that both correctness is guaranteed and worst-case (or average-case) performance is optimized. Correctness is formalized as race freedom or linearizability. We show that for worst-case performance, the problem can be modeled as a 2-player graph game with quantitative (limit-average) objectives, and for average-case performance, as a 2 1/2 -player graph game (with probabilistic transitions). In both cases, the optimal correct program is derived from an optimal strategy in the corresponding quantitative game. We prove that the respective game problems are computationally expensive (NP-complete), and present several techniques that overcome the theoretical difficulty in cases of concurrent programs of practical interest. We have implemented a prototype tool and used it for the automatic syn- thesis of programs that access a concurrent list. For certain parameter val- ues, our method automatically synthesizes various classical synchronization schemes for implementing a concurrent list, such as fine-grained locking or a lazy algorithm. For other parameter values, a new, hybrid synchronization style is synthesized, which uses both the lazy approach and coarse-grained locks (instead of standard fine-grained locks). The trade-off occurs because while fine-grained locking tends to decrease the cost that is due to waiting for locks, it increases cache size requirements

Folding regulates autoprocessing of HIV-1 protease precursor

Autoprocessing of HIV-1 protease (PR) precursors is a crucial step in the generation of the mature protease. Very little is known regarding the molecular mechanism and regulation of this important process in the viral life cycle. In this context we report here the first and complete residue level investigations on the structural and folding characteristics of the 17-kDa precursor TFR-PR-Cnn (161 residues) of HIV-1 protease. The precursor shows autoprocessing activity indicating that the solution has a certain population of the folded active dimer. Removal of the 5-residue extension, Cnn at the C-terminal of PR enhanced the activity to some extent. However, NMR structural characterization of the precursor containing a mutation, D25N in the PR at pH 5.2 and 32 °C under different conditions of partial and complete denaturation by urea, indicate that the precursor has a high tendency to be unfolded. The major population in the ensemble displays some weak folding propensities in both the TFR and the PR regions, and many of these in the PR region are the non-native type. As both D25N mutant and wild-type PR are known to fold efficiently to the same native dimeric form, we infer that TFR cleavage enables removal of the non-native type of preferences in the PR domain to cause constructive folding of the protein. These results indicate that intrinsic structural and folding preferences in the precursor would have important regulatory roles in the autoprocessing reaction and generation of the mature enzyme

Structural characterization of the large soluble oligomers of the GTPase effector domain of dynamin

Dynamin, a protein playing crucial roles in endocytosis, oligomerizes to form spirals around the necks of incipient vesicles and helps their scission from membranes. This oligomerization is known to be mediated by the GTPase effector domain (GED). Here we have characterized the structural features of recombinant GED using a variety of biophysical methods. Gel filtration and dynamic light scattering experiments indicate that in solution, the GED has an intrinsic tendency to oligomerize. It forms large soluble oligomers (molecular mass > 600 kDa). Interestingly, they exist in equilibrium with the monomer, the equilibrium being largely in favour of the oligomers. This equilibrium, observed for the first time for GED, may have regulatory implications for dynamin function. From the circular dichroism measurements the multimers are seen to have a high helical content. From multidimensional NMR analysis we have determined that about 30 residues in the monomeric units constituting the oligomers are flexible, and these include a 17 residue stretch near the N-terminal. This contains two short segments with helical propensities in an otherwise dynamic structure. Negatively charged SDS micelles cause dissociation of the oligomers into monomers, and interestingly, the helical characteristics of the oligomer are completely retained in the individual monomers. The segments along the chain that are likely to form helices have been predicted from five different algorithms, all of which identify two long stretches. Surface electrostatic potential calculation for these helices reveals that there is a distribution of neutral, positive and negative potentials, suggesting that both electrostatic and hydrophobic interactions could be playing important roles in the oligomer core formation. A single point mutation, I697A, in one of the helices inhibited oligomerization quite substantially, indicating firstly, a special role of this residue, and secondly, a decisive, though localized, contribution of hydrophobic interaction in the association process