The Institute of Science
The Institute of Science
News Article | May 4, 2017
Postdoc Joël Alwen and Professor Krzysztof Pietrzak -- together with their US collaborators -- have been awarded the best paper award at the Eurocrypt '17 conference. Their prize-winning work proves the existence of "memory-hard" functions, cryptographic functions that are designed to be "egalitarian" in the sense that they can't be computed at lower cost on dedicated hardware as compared to standard CPUs. These functions are crucial to securing password servers and have applications in the next generation of decentralized cryptocurrencies. A server will usually not store a user's password in the clear, but will instead apply a cryptographic hash function to it and store only the output, known as the hash value. This way a server can still verify a password by applying the hash function and checking if the output is the same as the stored value. However, if the password file is stolen -- something "which unfortunately seems to happen pretty much constantly," says Pietrzak -- the passwords are not immediately compromised: To find the password corresponding to a hash value, the adversary must hash different password candidates until the hash matches the stored value. For a typical human-generated password this requires hashing in the order of a billion values. Unfortunately a billion is not really much, so to make the adversaries task even harder, one uses a "moderately hard" hash function, which is expensive, but not too expensive, to compute -- this is not much of a burden for the server, who computes the function once per login attempt, but should make computing billions of hashes extremely costly for the adversary. The classical approach towards constructing moderately hard functions is to simply iterate a standard hash function a few thousand times. Unfortunately, this does not gain nearly as much security as one might hope: while servers use standard CPUs, an adversary can use special-purpose hardware on which evaluating such functions is several orders of magnitude cheaper in terms of hardware and energy cost. Thus brute-forcing passwords was nowhere near as costly as anticipated! To address this problem, in 2009, Colin Percival put forth the notion of "memory-hard" functions (MHFs)--moderately hard functions whose evaluation cost is dominated by memory cost. MHFs would be egalitarian: as memory cost is about the same over different hardware platforms, having special hardware would no longer benefit the adversary. Moreover, Percival also proposed a candidate MHF called scrypt, which became widely deployed. A first formal definition capturing memory-hardness (called parallel cumulative memory complexity) was only given six years later, in 2015, by IST Austria postdoc Joël Alwen and Vladimir Serbinenko of ETH Zurich. A variety of candidate MHFs--including a winner of a two-year password-hashing competition--were shown to not meet this definition. The status of Percival's original function scrypt, however, remained unresolved. In 2016, the cryptography groups at IST Austria and the University of California Santa Barbara presented initial progress in this direction. Now, a year later, together with Leonid Reyzin of Boston University -- who in 2016 spend a sabbatical at IST Austria -- they have succeeded in making the final steps, and have finally proved that scrypt is memory-hard. Their result, which will be presented in Paris at this year's Eurocrypt conference -- one of the two main cryptography conferences -- enhances our understanding of memory-hard functions in general, and scrypt in particular. This not only increases our trust in using scrypt for password hashing, but also a variety of decentralized cryptocurrencies, such as Litecoin and Dogecoin, already make use of scrypt. "This line of research still holds many exciting open problems that we are currently working on" says Pietrzak, "for example, the current models only capture hardware cost, but achieving egalitarianism in terms of energy cost is not yet well understood." Joël Alwen joined IST Austria as a postdoc in 2014, and has interests ranging from lattice-based cryptography to leakage resilience. He has also been involved a variety of programming projects, including the Netflix Challenge and designing attacks on password hashing functions. Professor Krzysztof Piertzak has headed the cryptography group at IST Austria since 2011, and explores a broad range of theoretical and practical aspects of cryptography, including memory-hard functions, cryptography for lightweight devices, symmetric cryptography, and sustainable cryptocurrencies. The Institute of Science and Technology (IST Austria) is a PhD granting research institution located in Klosterneuburg, 18 km from the center of Vienna, Austria. Inaugurated in 2009, the Institute is dedicated to basic research in the natural and mathematical sciences. IST Austria employs professors on a tenure-track system, postdoctoral fellows, and doctoral students at its international graduate school. While dedicated to the principle of curiosity-driven research, the Institute owns the rights to all scientific discoveries and is committed to promote their use. The first president of IST Austria is Thomas A. Henzinger, a leading computer scientist and former professor at the University of California in Berkeley, USA, und der EPFL in Lausanne, Switzerland.
Phapale R.,The Institute of Science |
Thakur S.M.,The Institute of Science
International Journal of Pharmacy and Pharmaceutical Sciences | Year: 2010
Feronia limonia (L.) Swingle fruit is much used in India as a stomachic, diuretic, cardiotonic and tonic to the liver and lungs. In this study, free and bound phenolic compound extracts were obtained by successive extractions of feronia limonia ripe fruit pulp. Total phenolic content was evaluated following Folin-Ciocalteu method; antioxidant activity by the DPPH assay and antimutagenic potential by the Ames test. The phenolic glycoside extract presented higher (229.0 mg/g, GAE) total phenolic contents followed by phenolic ester (37.5 mg/g) and free phenolics (11.0mg/g). Where as the antioxidant activity was 88.7%, 11.8% and 3.8% respectively. Phenolic glycoside extract showed antioxidant activity higher than that of commercial antioxidant Trolox (64.6%) and Butylated hydroxytoluene (83.2%). At 2500 μl/plate a significant antimutagenic effect was shown by phenolic glycoside extract and the order of antimutagenic activity was found phenolic glycosides > phenolic esters > free phenolics. Results indicated good correlation between total phenol content, antioxidant activity and antimutagenic effect. Phenolic glycosides in feronia limonia ripe fruit pulp showed promising antioxidant activity, antimytagenic effect and needs further exploration for their effective use in both modern and traditional system of medicines.
Singh R.,The Institute of Science |
Mendhulkar V.D.,The Institute of Science
International Journal of PharmTech Research | Year: 2015
Abutilon indicum, an important medicinal plant is a good source of various natural metabolites that has hepatoprotective, antitumor, anti-inflammatory, lipid lowering, antifungal, wounds healing and antibacterial properties. Present study was aimed to evaluate the saponin content in leaves of A. indicum, spectrophotometrically. A indicum leaves showed good saponin yield i.e. about 30 %. Spectrophotometric analysis of crude extracted from dried leaves, showed 296 mg of total saponin and 7.0 mg of steroidal saponin, diosgenin equivalent (DE) per gm of crude extract. This indicated that A. indicum plants leaves contained high level of saponin and could be regarded as potential natural source of it, which could feasibly be utilized for a variety of commercial purposes. In addition, they can be used in ethnomedicine as drugs against viral, bacterial, fungal infections and to synthesize sex hormones, oral contraceptives and drugs to cure various serious diseases of human being. © 2015, Sphinx Knowledge House. All rights reserved.
Saraf A.,The Institute of Science |
Sankhla S.,The Institute of Science
International Journal of Pharmacognosy and Phytochemical Research | Year: 2015
Tecomella undulata (Seem), family Bignoniaceae, is an important medicinal plant found in western region of India and traditionally used in indigenous system of medicine. An attempt has been made to give a complete HPTLC profile for leaf, bark and flower of Tecomella undulata (Seem). Methanolic, chloroform and acetone extracts were prepared using sonication. The mobile phase of Toluene: Ethyl acetate: Formic acid was used in different ratio for good separation. The fingerprint showed better resolution after derivatisation in methanolic sulphuric acid reagent. The fingerprint has revealed a distinct and repetitive pattern of bands. Acetone extract of leaf and bark shows 14 different Rf values whereas flower shows maximum separation in chloroform. HPTLC profile of the plant will be helpful for crude drug identification, serve to check the adulteration and also act as biomarker for this plant in the Pharmaceutical industry. © 2015, International Journal of Pharmacognosy and Phytochemical Research. All rights reserved.
Lavand A.B.,The Institute of Science |
Malghe Y.S.,The Institute of Science
Journal of Saudi Chemical Society | Year: 2015
C/ZnO/CdS nanocomposite was synthesized using the microemulsion method. Nanocomposite synthesized in the present work was characterized using X-ray diffractometer (XRD), scanning electron microscope (SEM), energy dispersive X-ray spectroscopy (EDX) transmission electron microscope (TEM), diffuse reflectance and photoluminescence (PL) spectroscopy. TEM study shows that CdS nanoparticles are successfully anchored on the surface of C doped ZnO nanorods. UV-visible spectrum of C/ZnO/CdS nanocomposite shows a red shift. CdS nanoparticles work as photo sensitizers to expand the photo-response of C doped ZnO to the visible region. Photoluminescence (PL) spectroscopy reveals evidence for interaction between C/ZnO and CdS. PL quenching observed for C/ZnO/CdS nanocomposite is attributed to improved charge separation properties, which increases its photocatalytic efficiency. C/ZnO/CdS nanocomposite exhibits exceptionally high photocatalytic activity for degradation of 4-chlorophenol (CP) via Z-scheme mechanism. C/ZnO/CdS nanocomposite is a highly stable and reusable photocatalyst. © 2015 King Saud University.
Alphonso P.,The Institute of Science |
Saraf A.,The Institute of Science
Asian Pacific Journal of Tropical Biomedicine | Year: 2012
Objective: To establish the chemical fingerprint of various secondary metabolites of Zanthoxylum rhetsa (Roxb.) DC, a medicinally important plant. Methods: Preliminary phytochemical screening for various secondary metabolites was carried out. HPTLC profiles of various individual secondary metabolites were done and profiles were developed for authentication. Result: The ethanolic extract of the fruit showed the presence of 8 Glycosides, 10 Flavonoids, 6 Essential Oils, 5 Anthraquinones, 9 bitter principles, 7 Coumarins and 8 Terpenoids. Conclusions: The development of such fingerprint for the fruits of Zanthoxylum rhetsa (Roxb.) DC is useful in differentiating the species from the adulterant and also act as biomarker for this plant in the Pharmaceutical industry. © 2012 Asian Pacific Tropical Biomedical Magazine.
Lavand A.B.,The Institute of Science |
Malghe Y.S.,The Institute of Science
Advanced Materials Letters | Year: 2015
Nanosized bare and carbon (C)-doped TiO2 were prepared using reverse micro-emulsion method. Synthesized powders were characterized with the help of X-ray diffractometer (XRD), scanning electron microscope (SEM), transmission electron microscope (TEM), energy dispersive X-ray spectroscope (EDX) and UV-visible spectrophotometer. EDX study reveals that as calcination temperature increases amount of C on TiO2 decreases. SEM and TEM images show that TiO2 particles are spherical in shape and after increasing the calcination temperature size of particle increases. Particle size of TiO2 obtained from TEM data varies between 10 to 17nm. Visible light photocatalytic degradation of 2,4,6-trichlorophenol (TCP) aqueous solution was carried out using nanosized bare as well as C-doped TiO2. UV-visible spectrophotometer and high pressure liquid chromatography (HPLC) techniques were used to analyze the concentration of TCP during the degradation process. In presence of visible light C-doped TiO2 obtained after calcination of precursor at 300°C shows better photocatalytic activity. Parameters affecting the photocatalytic process such as calcination temperature, amount of catalyst and TCP concentration are investigated. TCP photocatalytic degradation process was optimized. It is observed that to get better photocatalytic activity optimum amount of photocatalyst and concentration of TCP solution required are 1.0 gL-1 and 20 mg L-1 respectively. Reusability study indicates that C doped TiO2 prepared in the present work is highly stable and reusable photo catalyst. © 2015 VBRI Press.
Kalamse V.,S R T M University |
Wadnerkar N.,S R T M University |
Chaudhari A.,The Institute of Science
Energy | Year: 2013
A density functional study of hydrogen uptake capacity of multi-functionalized naphthalene with Ti and Li metal atom has been carried out. It is observed that, the naphthalene functionalized with two Ti atoms can interact with total eight hydrogen molecules in which each Ti metal atom interacts with four hydrogen molecules. Naphthalene decorated with two Li atoms can interact with total three H2 molecules only. First (19Li) and second (20Li) Li atom can interact with only one and two hydrogen molecule respectively. It is observed that, hydrogen molecules bind strongly to the C10H8Ti2 complex than C10H8Li2 complex. The gravimetric hydrogen uptake capacity of C10H8Ti2 and C10H8Li2 complex is found to be 6.72 and 3.73 wt% respectively. Moreover, after functionalizing naphthalene with four Li atoms, the uptake capacity is increased to 7.20 wt %. However, the thermochemistry result favors to Ti functionalized naphthalene complex (C10H8Ti2) for hydrogen storage over Li functionalized naphthalene (both C10H8Li2 and C10H8Li4) complexes. Atom-centered density matrix propagation (ADMP) molecular dynamics simulations have been performed which showed that C10H8Li2 and C10H8Li4 complex cannot bind single hydrogen molecule at room temperature whereas C10H8Ti2 can bind five hydrogen molecules. © 2012 Elsevier Ltd.
Mendhulkar V.D.,The Institute of Science |
Kharat S.N.,The Institute of Science
International Journal of Pharma and Bio Sciences | Year: 2015
The High Performance Thin Layer Chromatography (HPTLC) was carried out for the estimation of flavonoid content in the medicinal plant Elephantopus scaber [Linn], grown under heat stress conditions. The experimental plant system was subjected to the Heat Stress Induced (HSI) condition for two hours at 40 °C temperature daily for 7 days. Plants grown in Green House condition was taken as a control (GHC). The plant extracts were prepared in ethanol, methanol and water solvent system using sonication and maceration as variable extraction methods, independently. The mobile phase used was ethyl acetate: acetic acid: formic acid: water [100:11:11:27 v/v/v/v]. Detection and quantification was performed densitometrically at the wavelength of 254 nm and 366 nm for standard and all the plant samples, respectively. Our analysis in studying experimental system indicated remarkable fluctuations in the content of quercetin which ranges from 42.88 μg/ml (for GHC) to 143.74 μg/ml (for HSI). For the rutin, range was varying from 25.98 μg/ml (for GHC) to 49.43 μg/ml of plant material (for HSI). These findings provided the insight to understand the quantitative interference in secondary metabolites caused by stress conditions. In the present investigation the fluctuations in the flavonoid contents of the plant grown under stress condition were analyzed and the results obtained are discussed.
Naganathappa M.,Dr. Babasaheb Ambedkar Marathwada University |
Chaudhari A.,The Institute of Science
Monthly Notices of the Royal Astronomical Society | Year: 2012
Polycyclic aromatic hydrocarbons (PAHs) or PAH-related molecules are considered to be responsible for the unidentified infrared (UIR) emission features at 3.3, 6.2, 7.7, 8.6 and 11.2 μm. However, the exact identification of PAH or PAH-related molecules is difficult. There have been several investigations on the spectroscopic characterization of PAH molecules. But none of them compared the spectra of isomers of PAHs, which might have help in the identification of the UIR emission features. This work presents the infrared and electronic absorption spectra of isomers of C 16H 10. The aim of the present work is to compare infrared and electronic absorption spectra of four isomers of C 16H 10 PAH viz. pyrene, aceanthrylene, acephenanthrylene and fluoranthene, their ions and doubly ions. We also compare the spectra of pyrene in the gas-phase and in H 2O ice. We have used the density functional theory with B3LYP exchange and correlation functional and 6-311++g** basis set to study the infrared spectra. The time-dependent density functional theory (TDDFT) has been used to obtain the electronic absorption spectra. Significant difference in the CC stretching, CH in-plane bending and CH out-of-plane bending vibration modes is observed for the isomers of C 16H 10 whereas there is no large difference in the CH stretching vibration band. A significant change in the vibrational band is observed for pyrene in H 2O ice compared to gas-phase pyrene. Though isomers of C 16H 10 PAH have the same number of carbon and hydrogen atoms, their spectroscopic characteristics are different. This study should help in identifying the isomers of C 16H 10, their ions and doubly cation in the interstellar medium. © 2012 The Authors Monthly Notices of the Royal Astronomical Society © 2012 RAS.