Anti Attack Research Articles

Research on blind watermarking algorithm of encrypted holographic 3d geographic information data based on mapping mechanism

In order to improve the accuracy and security of encrypted holographic 3D geographic information data acquisition and improve the actual resolution of geographic information files, a blind watermarking algorithm for encrypted holographic 3D geographic information data based on mapping mechanism is proposed. According to the characteristics of the mapping mechanism, a mapping mechanism structure diagram is constructed; Under the mapping mechanism technology, blind watermark data is preprocessed. Then, a watermark embedding operation is performed to obtain the watermark information image, and then a blind watermark that encrypts the holographic three-dimensional geographic information data is extracted. Finally, using the blind watermark signal as input, the blind watermark information is obtained by using the watermark strength, and the holographic 3D geographic data information is segmented and encrypted to complete blind watermark detection. The blind watermark algorithm for encrypting the holographic 3D geographic information data is studied. The results show that the maximum difference between the correlation coefficient of the algorithm in this paper and the correlation coefficient of the unaffected algorithm is only 0.04, which has better anti attack performance, high security, good terrain information collection ability, high data accuracy, and can achieve curvature repair of information data.

Advanced 5D logistic and DNA encoding for medical images

ABSTRACT Since patient diagnostic data such as X-rays, MRIs, CT scans, etc. contain very sensitive information about a patient's health, it must be encrypted to prevent unauthorized access. In chaotic-based image encryption methods, the lower-dimensional chaotic maps are insufficient because they can be estimated through some signal estimation technologies; therefore, a higher-order novel 5D logistic chaotic map along with DNA encoding and the Arnold map for medical image encryption is presented to overcome the vital medical breaching that could cost a life. In this work, the advantages of DNA principles and high-dimensional chaotic maps are used to develop an efficient encryption method for the protection of medical images. The strategy is useful due to the fact that the higher order makes the system more complicated and tough to penetrate. The large keyspace up to, anti attack capabilities, and comparison of various standard parameters with different literatures illustrate the algorithm's superiority.

Empirical Analysis of Robust Chaotic Maps for Image Encryption

The rate of transferring data in the form of text, image, video or audio over an open network has drastically increased. As these are carried out in highly sophisticated fields of medicine, military and banking, security becomes important. In- order to enhance security for transmission, encryption algorithms play a vital role. So as to enhance the proficiency of the existing encryption methods and for stronger anti attack abilities, chaotic based cryptography is essential. Chaotic based encryption has advantages of being sensitive to initial conditions and control parameters. Images have features like bulk data capacity and high inter pixel correlation. Transmission of such medical data should be highly confidential, integral and authorized. Hence chaos-based image encryption is an efficient way of fast and high-quality image encryption. It has features like good speed, complexity, highly secure, reasonable computational overhead and power. In this paper a comprehensive analysis and an evaluation regarding the capabilities of different discrete time domain chaotic maps were carried out on a proposed image encryption method. The experimental results show high efficiency for the proposed image encryption technique.

Encryption technology of voice transmission in mobile network based on 3DES-ECC algorithm

The traditional design of voice collector has poor anti attack ability, which makes the encryption effect of voice transmission poor. Therefore, taking the mobile network voice collector as the research object, 3des-ecc algorithm is applied to the information transmission encryption of the mobile network voice collector.An improved speech signal collector is designed, which combines 3DES and ECC algorithm to realize the encryption of speech transmission information. An improved voice signal collector is designed, which combines 3DES and ECC algorithm to realize the encryption of voice transmission information. In the process of encryption, 168-bit random key is generated first, and it is grouped according to 56 bits as 3DES key, and then the plaintext is encrypted by the key to generate ciphertext; the random key is encrypted by ECC public key of the receiver. The experimental results show that the encryption time of this method is less than 1 s, the data integrity is 93%, and the data loss rate is only 0.33%. It has better anti attack ability, fast encryption speed and good encryption effect.

An Anti-Gray Hole Attack Scheme in Mobile Ad Hoc Network

Dynamic variation of network topology in mobile ad hoc networks (MANET) forces network nodes to work together and rely on each other for routing. Considering the lack of a central control node, some nodes appear maliciously and selectively drop the data packets instead of transmitting to the next hop node, which is known as the gray hole attack. In order to prevent and identify the gray hole attack, an intrusion detection system (IDS) is proposed on nodes to maintain network efficiency. In addition to establishing security, the proposed anti gray hole attack mechanism extracts abnormal differences between routing packets in the route discovery phase of the ad hoc on-demand distance vector (AODV) routing protocol. It then assigns a suspicious value to each participating node and monitors the exchange of data packets between neighboring nodes in the data transfer phase using a data transmission information table. If the suspicious value reaches a predetermined threshold, IDS nodes send an alert message to other nodes about the identity of the malicious node, in order to prevent its activity on the network. Simulation results indicate that the performance of the proposed scheme in terms of packet delivery rate, packet loss rate, and routing overhead outperforms those in the literature.

Asymmetric Three‐Component Heck Arylation/Amination of Nonconjugated Cyclodienes

AbstractSubstituted cyclohexylamines are becoming increasingly important in drug discovery. Asymmetric Heck insertion/amination of nonconjugated cyclodienes proceeds to give 5‐aryl cyclohexenylamines with good enantioselectivity and exclusive trans configurations. Primary and secondary anilines, indoline, and benzylamines are suitable amines. The weakly donating diphosphite Kelliphite forms a deep unsymmetrical pocket, which is essential for stereoselective anti attack of amines.

Asymmetric Three-Component Heck Arylation/Amination of Nonconjugated Cyclodienes.

Substituted cyclohexylamines are becoming increasingly important in drug discovery. Asymmetric Heck insertion/amination of nonconjugated cyclodienes proceeds to give 5-aryl cyclohexenylamines with good enantioselectivity and exclusive trans configurations. Primary and secondary anilines, indoline, and benzylamines are suitable amines. The weakly donating diphosphite Kelliphite forms a deep unsymmetrical pocket, which is essential for stereoselective anti attack of amines.

User Privacy Protection Algorithm Of Perceptual Recommendation System Based On Group Recommendation

In order to overcome the problems of low recommendation quality and poor privacy protection ability of existing user privacy protection algorithms. This paper proposes a new privacy protection algorithm based on group recommendation. The general model of recommender system is analysed by user modelling, recommender object modelling and recommender algorithm, and the privacy concerns of perceptual recommender system are analysed by questionnaire. Based on the classification of user privacy concerns, group recommendation is introduced, and the user data is submitted anonymously through the anonymous nature of senders provided by crowds network, so as to prevent the server and malicious users from identifying good users and complete the research of protection algorithm. The experimental results show that the proposed algorithm has good recommendation quality, the highest recommendation accuracy of 99%, and high anti attack success rate and reliability.

A blind watermarking algorithm based on adaptive quantization in Contourlet domain

Aiming at the copyright protection of digital works, a blind watermarking algorithm in Contourlet domain based on adaptive quantization is proposed. The algorithm adaptively regulates quantization step size in the Contourlet domain according to the mean of each sub block, so that the embedding strength of watermark can better adapt to the characteristics of each sub block. Before extracting watermark, the rotation correction algorithm has been applied in processing image, which greatly improves the ability of blind watermarking algorithm to resist rotation attacks. Many anti attack experiments are carried out on the proposed algorithm. The results show that the algorithm has good robustness, and it has distinctness advantages in anti JPEG compression, Gauss noise, shear and rotation attack.

ChemInform Abstract: Synthesis of Polysubstituted 2‐Iodoindenes via Iodonium‐Induced Cyclization of Arylallenes.

AbstractA new chemo‐ and regioselective iodocarbocyclization of allenylarenes is presented.

Mechanistic insights into hydrogen generation for catalytic hydrolysis and alcoholysis of silanes with high-valent oxorhenium(v) complexes

The ionic outer-sphere pathway, which proceeds via the nucleophilic anti attack of water or alcohol on the silicon atom is the most favorable pathway for the high-valent oxorhenium(v) complex-catalyzed hydrolysis/alcoholysis of organosilanes.

An Improved QIM Watermarking Algorithm

Put forward an improved QIM watermark embedding algorithm. The carrier image is transformed into YCbCr space, lifting wavelet transform the three components, then using the QIM quantization method embeds watermark into high frequency coefficients of Cb and Cr component, and Y component of low frequency coefficients. The experimental results show that embedded watermark which using improved algorithm has good invisibility. Anti attack test results show that after using common attack method attack the image embedded watermark, it can still extract the watermark completely. The anti-attack performance of improved QIM algorithm is much better than texture watermarking algorithm based on DCT.

Transition-Metal Catalysis with Hollow-Shaped Triethynylphosphine Ligands

Abstract Triethynylphosphines with bulky end caps such as triarylsilyl and triarylmethyl groups at alkyne termini have a novel molecular shape presenting a large, deep metal-binding cavity. The hollow-shaped triethynylphosphines functioned as effective ligands in the rhodium-catalyzed hydrosilylation of ketones with triorganosilanes due to the preferential formation of a mono-P-ligated rhodium species. Furthermore, the phosphines displayed remarkable rate enhancement in the gold(I)-catalyzed alkyne cyclization constructing six- to eight-membered ring compounds. It is proposed that the cavity in the ligand forces a nucleophilic center of the acetylenic compounds close to the gold-bound alkyne, making ring-closing anti attack feasible.

Research of the Wavelet Transform Printing Forgery Prevention Algorithm Based on Chaotic Characteristics

From the prospect of the printing forgery prevention technology, this paper systematically analyzed the principles of digital watermark in printing forgery prevention technology, based on this, it proposed wavelet transforming printing forgery prevention algorithm based on chaotic characteristics, in this paper, by using digital watermark image scrambling technology based on chaotic mapping to encrypt the wavelet transforming coefficient, then choose the different K value in chaotic mapping and the size of the scrambling image to combine the the cryptography technology and the wavelet transforming technology for resisting the various printing forgery attack effectively. In the end, the author made a detailed design about the wavelet transform printing forgery prevention system which based on chaotic characteristics and put it into fact by VC++, then validated the algorithm by experimental result, then compared it to the traditional watermark algorithm from the aspect of the image compression and anti attack ability to prove the stability and robustness of the algorithm this paper proposed.

Hydrosilylation of Carbonyls Catalyzed by the Rhenium(V) Oxo Complex [Re(O)(hoz)2]+—A Non-Hydride Pathway

Catalytic conversion of silane and carbonyls by the cationic rhenium oxo complex [Re(O)(hoz)2]+ (1; hoz = 2-(2′-hydroxyphenyl)-2-oxazoline(1−)) was examined using density functional theory. It is shown that complex 1 catalyzed the carbonyl hydrosilylation via a non-hydride pathway—the ionic hydrogenation mechanism. The complete catalytic cycle is proposed to involve three steps: the formation of cis η1-silane Re(V) adduct, the heterolytic cleavage of a Si–H bond through anti attack of carbonyls at the cis η1-silane Re(V) adduct, and transfers between the rhenium and activated silylcarbonium ion to produce the silyl ether product and regenerate catalyst 1. The σ-bond metathesis like transition state suggested by Abu-Omar, although not located, can be inferred from the ionic hydrogenation transition states (TS_3syn and TS_5syn, in which the carbonyls syn attack the η1-silane Re(V) adduct) associated with the higher energy barrier.

Mechanism and Stereoselectivity of the Stepwise 1,3-Dipolar Cycloadditions between a Thiocarbonyl Ylide and Electron-Deficient Dipolarophiles: A Computational Investigation

The 1,3-dipolar cycloadditions of a thiocarbonyl ylide to dimethyl 2,3-dicyanofumarate and 2,3-dicyanomaleate have been studied with DFT computations. The first C-C bond is formed via an anti attack to produce a very polar, zwitterionic diradical. The low stereoselectivity of the reaction was found to arise from rotations about single bonds in the intermediates that compete with cyclization. A distortion-interaction energy analysis was performed to compare the stepwise and concerted mechanisms, and to explain why the stepwise mechanism is favored in this unusual case.

Mechanistic Aspects of Nucleophilic Substitution at Half-Sandwich Metal Complexes

The hydrolysis reactions of organometallic ruthenium(II) piano-stool complexes of the type [RuII(η6-cymene)(L)Cl]0/+ (1−5, where L = κ1- or κ2-1,1-bis(diphenylphosphino)methane, 1,1-bis(diphenylphosphino)methane oxide, κ1-mercaptobenzothiazole) have been studied using density functional theory at the B3LYP level. In addition to considering a syn attack in an associative fashion, where the nucleophile approaches from the same side as the leaving group, we have explored alternative paths such as an anti attack in an associative manner, where the nucleophile attacks from the opposite side of the leaving group. During the anti attack, an intermediate is formed and there is a coordination mode change of the arene ring from η6 to η2 along with its rotation. When the intermediate goes to the product, the arene ring slips back from η2 to η6 coordination. This coordinated movement of the arene ring makes the associative anti attack an accessible pathway for the substitution process. Our calculations predict very s...

Mechanism and Kinetics of the Wacker Process: A Quantum Mechanical Approach

Study of the mechanism of the Wacker oxidation is of great importance for many reasons. Thus far, from a theoretical point of view, particularly in connection with the rate-determining step, no mechanism has been presented which includes all experimental evidence, notably the isotopic effect, the energy barrier, and the rate constant of the reaction. In this work, we proposed a mechanism for nucleophilic addition which quantitatively and qualitatively will be in good agreement with the experimental evidence. The mechanism study of the Wacker process has been performed using a density functional method in the gas and solution (Onsager and PCM models) phases. The internal nucleophilic addition of the OH group on the coordinated alkene has been investigated as a direct attack or water chain attack. The reaction progress in both routes of syn and anti attack yields two different products for this step; therefore, modeling of attacks has been performed for both routes. The results obtained in the gas and solut...

SN2′ Alkylation of Chiral Allylic Cyanohydrin O‐Phosphates with Organocuprates

AbstractEnantiomerically enriched cyanohydrin O‐phosphates, prepared by enantioselective cyanophosphorylation of α,β‐unsaturated aldehydes, react regioselectively at the γ‐position with organocuprates derived from alkyl Grignard reagents and CuCN to afford chiral γ‐alkyl‐substituted α,β‐unsaturated nitriles. The configuration of the new C–C double bond is mainly (E) when the reaction is performed at –78 °C and (Z) when it is carried out at higher temperatures (0 °C). A high level of transfer of the chirality in the new stereocentre, corresponding to a stereospecific anti attack onto the cyanophosphate, is observed. Enantiomerically enriched (E)‐γ‐alkylated α,β‐unsaturated esters are prepared after subsequent methanolysis in a three‐step sequence from the corresponding α,β‐unsaturated aldehydes. In addition, the synthesis of (R)‐4‐methylnonan‐1‐ol, also known as the sex pheromone of the yellow mealworm Tenebrio molitor L, and its (S) enantiomer have been carried out in a four‐step route from (E)‐oct‐2‐enal. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007)

Stereoselective Aza Diels−Alder Reaction on Solid Phase: A Facile Synthesis of Hexahydrocinnoline Derivatives

As part of our continuing studies of polymer-supported pericyclic reactions for preparing biologically interesting heterocyclic compounds, we have introduced a traceless solid-phase synthesis of hexahydrocinnolines. We developed a method in which mild reaction conditions can be used for the hetero-Diels-Alder reactions on a polymeric support. The dienoic 3-vinyl-2-cyclohexenol attached to a Wang resin through an ether linkage undergoes [4 + 2] cycloaddition reaction with several azadienophiles. The highly stereoselective Diels-Alder reaction showed preferential formation of a single cycloadduct resulting from an anti attack of the dienophile on the polymer-bound diene. Trifluoroacetic acid-mediated cleavage of the polymer-bound cycloadducts yields fused nonaromatic hexahydrocinnolines in moderate yields in three steps.