Cryptanalysis of an iterated halving-based hash function: CRUSH

Iterated Halving has been suggested as a replacement to the Merkle?Damga?rd (MD) construction in 2004 anticipating the attacks on the MDx family of hash functions. The CRUSH hash function provides a specific instantiation of the block cipher for Iterated Halving. The authors identify structural problems with the scheme and show that they can trivially identify collisions and second preimages on many equal-length messages of length ten blocks or more. The cost is ten decryptions of the block cipher, this being less than the generation of a single digest. In addition, these attacks can be used to differentiate CRUSH from a random oracle in O(1). The authors show that the complexity of finding a preimage in the unpadded CRUSH with the length encoding is negligible and extend this attack on CRUSH with the length encoding in cost O(2/sup 32/). This attack is a multi-preimage attack, since the attacker can produce a large number of messages for a given message digest for the cost of O(2/sup 32/). Hence, this attack can be used as a multi-collision and a multisecond- preimage as well. They show that if the attacker knows the last 64-bits of the message digest in advance, he can do the time-consuming part of the attack off-line. The authors show that even if Iterated Halving is repaired, the construction has practical issues that means it is not suitable for general deployment.     

Mathematics for reasoning about loop functions

The criticality of modern software applications, the pervasiveness of malicious code concerns, the emergence of third-party software development, and the preponderance of program inspection as a quality assurance method all place a great premium on the ability to analyze programs and derive their function in all circumstances of use and all its functional detail. For C-like programming languages, one of the most challenging tasks in this endeavor is the derivation of loop functions. In this paper, we outline the premises of our approach to this problem, present some mathematical results, and discuss how these results can be used as a basis for building an automated tool that derives the function of while loops under some conditions.     

Electropolymerization and characterization of polyaniline, poly(2-anilinoethanol) and poly(aniline-co-2-anilinoethanol)

Applications of conducting polymers to biosensors have recently aroused much interest. This is because these molecular electronic materials offer control of different parameters such as polymer layer thickness, electrical properties and bio-reagent loading, diversity, ease of fabrication and potentially low cost, etc. Polyaniline, poly(2-anilinoethanol) and poly(aniline-co-2-anilinoethanol) preparations are performed with electrochemical (CV) method at room temperature, in a standard three-electrode cell. Homopolymer and the copolymers of aniline and 2-anilinoethanol films were deposited from 1?M acidic aqueous media containing 0.2?M aniline, 2-anilinoethanol by voltammetric sweep between ?0.1 and 1 V Ag/AgCl, at 20?mV/s^?1. The sweep was stopped after 30 cycles at ?0.1?V Ag/AgCl and the working electrode was covered by homopolymer and copolymer of aniline and 2-anilinoethanol. Characterizations of the products were carried out by cyclic voltammograms, UV?Cvisible, differential scanning calorimetry (DSC), Fourier transform infrared spectroscopy (FTIR) and electrochemical impedance (EIS) was employed to examine the water absorption of the synthesized polymers to be used in biosensor application. Electrochemical properties of polyaniline, poly(2-anilinoethanol) and poly(aniline-co-2-anilinoethanol) were studied and it is shown that with increased (2-anilinoethanol) content in the copolymer, its electroactivity, conductivity and resistance are reduced, though the processability and adhesion properties improve. The hydrophilicity of polymer film obtained has increased with increasing (2-anilinoethanol) content which leads to salt moving to the surface of steel.     

Effect of single and multi-channel electrodes application on EDM fast hole drilling performance

In diesel engines, it is inevitable that the torsional vibration is produced by the fluctuation of engine torque. Therefore, it is necessary to establish preventive measures to diminish the torsional vibration. A sleeve spring damper is one such measure to reduce the torsional vibration. In this study, the closed form equations to predict the spring constant of a sleeve spring and the dynamic characteristics of the torsional vibration damper are proposed to calculate stiffness of the damper, and verified their availability through the finite element analysis. Our theoretical values are in good agreement with results obtained from finite element analysis and experiments. Results obtained from the derived equation enable designers to be more efficient.     

Heavy Metals In Water,Suspended Particles,Sediments And Aquatic Plants Of Habbaniya Lake,Iraq

Seasonal samples were taken from four selected stations on the Habbaniya lake, middle of Iraq during 1997, to study six heavy metals (Cu, Cd, Pb, Ni, Mn, and Zn), in water suspended particles, sediments and aquatic plants. Five plant species were collected, represented the most dominant in the lake, namely Myriophyllum verticillatum, Potamogeton crispus, P. pectinatus, Ceratophyllum demersum and Vallisnaria spiralis . Zn had the highest concentration among the studied metals in filtered water and suspended particles with an average of 4.08 w g/l and 26088 w g/g, respectively. Whereas, Mn had the highest in the sediments and all studied aquatic plants, which ranged between 213.3- 2027 w g/g and 100-1725 w g/g, respectively, Meanwhile, Cd had the lowest concentration in all studied samples.     

Synthesis and surface properties of polydimethylsiloxane‐based block copolymers: poly[dimethylsiloxane‐block‐ (ethyl methacrylate)] and poly[dimethylsiloxane‐block‐(hydroxyethyl methacrylate)]

A polydimethylsiloxane (PDMS) macroazoinitiator was synthesized from bis(hydroxyalkyl)‐terminated PDMS and 4,4′‐azobis‐4‐cyanopentanoic acid by a condensation reaction. The bifunctional macroinitiator was used for the block copolymerization of ethyl methacrylate (EMA) and 2‐(trimethylsilyloxy)ethyl methacrylate (TMSHEMA) monomers. The poly(DMS‐block‐EMA) and poly(DMS‐block‐TMSHEMA) copolymers thus obtained were characterized using Fourier transform infrared and ¹H NMR spectroscopy and differential scanning calorimetry. After the deprotection of trimethylsilyl groups, poly(DMS‐block‐HEMA) and poly(DMS‐block‐EMA) copolymer film surfaces were analysed using scanning electron microscopy and X‐ray photoelectron spectroscopy. The effects of the PDMS concentration in the copolymers on both air and glass sides of films were examined. The PDMS segments oriented and moved to the glass side in poly(DMS‐block‐EMA) copolymer film while orientation to the air side became evident with increasing DMS content in poly(DMS‐block‐HEMA) copolymer film. The block copolymerization technique described here is a versatile and economic method and is also applicable to a wide range of monomers. The copolymers obtained have phase‐separated morphologies and the effects of DMS segments on copolymer film surfaces are different at the glass and air sides. Copyright © 2010 Society of Chemical Industry     

Enhancement of hydrogen evolution at cobalt-zinc deposited graphite electrode in alkaline solution

Thin Co layers were electrochemically deposited on a graphite electrode at different deposition current densities and thicknesses. After determining the best deposition conditions for hydrogen evolution (deposition current density and thickness), co-deposits of Co with Zn were prepared on the graphite electrode. The binary coatings prepared on the graphite electrode (CoZn) were etched in a concentrated alkaline solution (30% NaOH) to produce a porous and electrocatalytic surface suitable for use in the hydrogen evolution reaction (HER). After the leaching process, a low amount of Pt was deposited onto the etched CoZn deposit in order to further improve the catalytic activity of the electrode for the HER. The HER activity is assessed by recording cathodic current-potential curves, electrochemical impedance spectroscopy (EIS) and electrolysis techniques. Chemical composition of layers after alkaline leaching was determined by energy dispersive X-ray (EDX) analysis. The surface morphologies of coatings were investigated by scanning electron microscopy (SEM). It was found that, the HER activity of coatings depends on the metal ratio of Co and Zn, deposition current density and the thickness of coatings. The alkaline leached CoZn coating has a compact and porous structure as well as good electrocatalytic activity for the HER in alkaline media. Moreover, deposition of a low amount of Pt over the CoZn can further enhance its hydrogen evolution activity.     

A Robust Peak-to-Average Power Ratio Reduction Scheme by Inserting Dummy Signals with Enhanced Partial Transmit Sequence in OFDM Systems

Peak-to-average power ratio (PAPR) is one of the main drawbacks in orthogonal frequency division multiplexing (OFDM) systems. High PAPR forces the power amplifier to back off in order to operate in its linear region, which degrades the power efficiency of the system. Several PAPR reduction techniques have been developed, but most of them have not considered both complexity and PAPR reduction. In this paper, a novel PAPR reduction scheme based on the insertion of dummy sequences to an enhanced partial transmit sequence is proposed. By applying this scheme the PAPR performance is enhanced compared to the conventional methods while the complexity is significantly reduced. Numerical analysis is carried out with OFDM signal and QPSK modulation.     

Chemical formation,characterization and properties of polycarbazole

Polycarbazole (PCz) was synthesized by chemical polymerization of carbazole in acetonitrile medium using ammonium persulfate as oxidant. The selection of solvent, concentration of the monomer, composition of the solvent, polymerization time, temperature, and pH were optimized to obtain better quality and yield of the polycarbazole. The synthesized polycarbazole was characterized by various techniques such as UV–Visible, FTIR, ¹H‐NMR, ¹³C‐NMR, COSY, NOESY, and XRD spectroscopy. The solubility of the polycarbazole was tested in various solvents. The thermodynamic stability of the polycarbazole was examined by DSC and TGA‐DTA analysis. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010