Assembly of Colloidal Aggregates by Electrohydrodynamic Flow: Kinetic Experiments and Scaling Analysis

Electric fields generate transverse flows near electrodes that sweep colloidal particles into densely packed assemblies. We interpret this behavior in terms of electrohydrodynamic motion stemming from distortions of the field by the particles that alter the body force distribution in the electrode charge polarization layer. A scaling analysis shows how the action of the applied electric field generates fluid motion that carries particles toward one another. The resulting fluid velocity is proportional to the square of the applied field and decreases inversely with frequency. Experimental measurements of the particle aggregation rate accord with the electrohydrodynamic theory over a wide range of voltages and frequencies

Beobachtungen des Kometen 1908 c (Morehouse)

n/

Electrochemically controlled growth and positioning of suspended collagen membranes

Two independently recognized in vitro polymer aggregation variables, electric field and pH, can be used in concert to produce suspended membranes from solutions of type I collagen monomers, without need of a supporting substrate. A collagen network film can form at the alkalineacidic pH interface created during the normal course of water electrolysis with parallel plate electrodes, and the anchoring location can be controlled by adjusting the bulk electrolyte pH. Electrosynthesized films remain intact upon drying and rehydration and function as ion separation membranes even in submillimeter channels. This approach could benefit lab-on-a-chip technologies for rational placement of membranes in microfluidic devices

Structure formation in binary colloids

A theoretical study of the structure formation observed very recently [Phys. Rev. Lett. 90, 128303 (2003)] in binary colloids is presented. In our model solely the dipole-dipole interaction of the particles is considered, electrohidrodynamic effects are excluded. Based on molecular dynamics simulations and analytic calculations we show that the total concentration of the particles, the relative concentration and the relative dipole moment of the components determine the structure of the colloid. At low concentrations the kinetic aggregation of particles results in fractal structures which show a crossover behavior when increasing the concentration. At high concentration various lattice structures are obtained in a good agreement with experiments.Comment: revtex, 4 pages, figures available from authors due to size problem

Machine-checked proofs for cryptographic standards indifferentiability of SPONGE and secure high-assurance implementations of SHA-3

We present a high-assurance and high-speed implementation of the SHA-3 hash function. Our implementation is written in the Jasmin programming language, and is formally verified for functional correctness, provable security and timing attack resistance in the EasyCrypt proof assistant. Our implementation is the first to achieve simultaneously the four desirable properties (efficiency, correctness, provable security, and side-channel protection) for a non-trivial cryptographic primitive.Concretely, our mechanized proofs show that: 1) the SHA-3 hash function is indifferentiable from a random oracle, and thus is resistant against collision, first and second preimage attacks; 2) the SHA-3 hash function is correctly implemented by a vectorized x86 implementation. Furthermore, the implementation is provably protected against timing attacks in an idealized model of timing leaks. The proofs include new EasyCrypt libraries of independent interest for programmable random oracles and modular indifferentiability proofs.This work received support from the National Institute of Standards and Technologies under agreement number 60NANB15D248.This work was partially supported by Office of Naval Research under projects N00014-12-1-0914, N00014-15-1-2750 and N00014-19-1-2292.This work was partially funded by national funds via the Portuguese Foundation for Science and Technology (FCT) in the context of project PTDC/CCI-INF/31698/2017. Manuel Barbosa was supported by grant SFRH/BSAB/143018/2018 awarded by the FCT.This work was supported in part by the National Science Foundation under grant number 1801564.This work was supported in part by the FutureTPM project of the Horizon 2020 Framework Programme of the European Union, under GA number 779391.This work was supported by the ANR Scrypt project, grant number ANR-18-CE25-0014.This work was supported by the ANR TECAP project, grant number ANR-17-CE39-0004-01

Attacks Only Get Better: How to Break FF3 on Large Domains

We improve the attack of Durak and Vaudenay (CRYPTO\u2717) on NIST Format-Preserving Encryption standard FF3, reducing the running time from $O(N^5)$ to $O(N^{17/6})$ for domain $Z_N \times Z_N$. Concretely, DV\u27s attack needs about $2^{50}$ operations to recover encrypted 6-digit PINs, whereas ours only spends about $2^{30}$ operations. In realizing this goal, we provide a pedagogical example of how to use distinguishing attacks to speed up slide attacks. In addition, we improve the running time of DV\u27s known-plaintext attack on 4-round Feistel of domain $Z_N \times Z_N$ from $O(N^3)$ time to just $O(N^{5/3})$ time. We also generalize our attacks to a general domain $Z_M \times Z_N$, allowing one to recover encrypted SSNs using about $2^{50}$ operations. Finally, we provide some proof-of-concept implementations to empirically validate our results

Microfluidic device for robust generation of two-component liquid-in-air slugs with individually controlled composition

Using liquid slugs as microreactors and microvessels enable precise control over the conditions of their contents on short-time scales for a wide variety of applications. Particularly for screening applications, there is a need for control of slug parameters such as size and composition. We describe a new microfluidic approach for creating slugs in air, each comprising a size and composition that can be selected individually for each slug. Two-component slugs are formed by first metering the desired volume of each reagent, merging the two volumes into an end-to-end slug, and propelling the slug to induce mixing. Volume control is achieved by a novel mechanism: two closed chambers on the chip are initially filled with air, and a valve in each is briefly opened to admit one of the reagents. The pressure of each reagent can be individually selected and determines the amount of air compression, and thus the amount of liquid that is admitted into each chamber. We describe the theory of operation, characterize the slug generation chip, and demonstrate the creation of slugs of different compositions. The use of microvalves in this approach enables robust operation with different liquids, and also enables one to work with extremely small samples, even down to a few slug volumes. The latter is important for applications involving precious reagents such as optimizing the reaction conditions for radiolabeling biological molecules as tracers for positron emission tomography

Indifferentiability for Public Key Cryptosystems

We initiate the study of indifferentiability for public key encryption and other public key primitives. Our main results are definitions and constructions of public key cryptosystems that are indifferentiable from ideal cryptosystems, in the random oracle model. Cryptosystems include Public key encryption, Digital signatures, Non-interactive key agreement. Our schemes are based on standard public key assumptions. By being indifferentiable from an ideal object, our schemes satisfy any security property that can be represented as a single-stage game and can be composed to operate in higher-level protocols