一类改进的混沌迭代加密算法

指出了最近提出的一类混沌迭代分组密码算法的缺陷,通过选择明文攻击可以恢复出置换后的明文.算法中二进制序列的产生只依赖于密钥,而与明文无关,从而使算法容易造成信息泄露并遭受攻击.基于此,给出了一种可以抵御选择明文攻击的安全性更高的算法. 关键词： 混沌 混沌密码 攻击 安全性     

非线性弦振动方程的Painlevé,B(a)icklund变换和孤子解的聚变

借助于计算机符号计算系统Maple,用Weiss,Tabor和Carnevale等人提出的WTC方法首次验证非线性弦振动方程具有Painlevé性质,并得到非线性弦振动方程的Bcklund变换,用Hirota直接方法分析非线性弦振动方程孤子解的聚变现象.     

Steganalysis and improvement of a quantum steganography protocol via GHZ4 state

Quantum steganography that utilizes quantum mechanical effect to achieve the purpose of information hiding is a popular topic of quantum information. Recently, El Allati et al. proposed a new quantum steganography using GHZ₄ state. Since all of the 8 groups of unitary transformations used in the secret message encoding rule change the GHZ₄ state into 6 instead of 8 different quantum states when the global phase is not considered, we point out that a 2-bit instead of a 3-bit secret message can be encoded by one group of the given unitary transformations. To encode a 3-bit secret message by performing a group of unitary transformations on the GHZ₄ state, we give another 8 groups of unitary transformations that can change the GHZ₄ state into 8 different quantum states. Due to the symmetry of the GHZ₄ state, all the possible 16 groups of unitary transformations change the GHZ₄ state into 8 different quantum states, so the improved protocol achieves a high efficiency.     

Steganalysis and improvement of a quantum steganography protocol via a GHZ4 state

Quantum steganography that utilizes the quantum mechanical effect to achieve the purpose of information hiding is a popular topic of quantum information. Recently, E1 Allati et al. proposed a new quantum steganography using the GHZ4 state. Since all of the 8 groups of unitary transformations used in the secret message encoding rule change the GHZ4 state into 6 instead of 8 different quantum states when the global phase is not considered, we point out that a 2-bit instead of a 3-bit secret message can be encoded by one group of the given unitary transformations. To encode a 3-bit secret message by performing a group of unitary transformations on the GHZ4 state, we give another 8 groups of unitary transformations that can change the GHZ4 state into 8 different quantum states. Due to the symmetry of the GHZ4 state, all the possible 16 groups of unitary transformations change the GHZ4 state into 8 different quantum states, so the improved protocol achieves a high efficiency.     

An improved image encryption algorithm based on chaotic maps

Recently, two chaotic image encryption schemes have been proposed, in which shuffling the positions and changing the grey values of image pixels are combined. This paper provides the chosen plaintext attack to recover the corresponding plaintext of a given ciphertext. Furthermore, it points out that the two schemes are not sufficiently sensitive to small changes of the plaintext. Based on the given analysis, it proposes an improved algorithm which includes two rounds of substitution and one round of permutation to strengthen the overall performance.     

Some new exact solutions to the Burgers--Fisher equation and generalized Burgers--Fisher equation

Some new exact solutions of the Burgers--Fisher equation and generalized Burgers--Fisher equation have been obtained by using the first integral method. These solutions include exponential function solutions, singular solitary wave solutions and some more complex solutions whose figures are given in the article. The result shows that the first integral method is one of the most effective approaches to obtain the solutions of the nonlinear partial differential equations.     

A Novel Quantum Covert Channel Protocol Based on Any Quantum Secure Direct Communication Scheme

By analyzing the basic properties of unitary transformations used in a quantum secure direct communication (QSDC) protocol, we show the main idea why a covert channel can be established within any QSDC channel which employs unitary transformations to encode information. On the basis of the fact that the unitary transformations used in a QSDC protocol are secret and independent, a novel quantum covert channel protocol is proposed to transfer secret messages with unconditional security. The performance, including the imperceptibility, capacity and security of the proposed protocol are analyzed in detail.     

一种基于时滞混沌的加密算法

基于半导体激光时滞混沌映射,提出一种新的加密算法.用Ikeda方程产生的二进制序列掩盖明文,对明文块做依赖于密钥的置换,并用传统的混沌加密方法加密.在每一轮加密过程中,都会用一个与混沌映射、明文和密文相关的随机数对时滞项做微扰,以提高算法的安全性;状态转移函数不仅与密钥相关,而且与本轮输入的明文符号以及上一轮输出的密文符号相关,有效地防止了选择明文/密文攻击.仿真实验表明,该算法可行、有效.     

一类反应扩散方程的精确解

运用首次积分法并借助计算机符号计算系统Mathematica得到了一类非线性反应扩散方程u_t-u_(xx) au βu~2 γu~3=0的精确解,其中既包括已知的类孤立波解,又有新的精确解.     

描述顺流方向可变剪切流动的一类变系数Boussinesq方程的Painlevé分析和相似约化

本文研究一类描述在顺流方向上存在可变剪切流动的长波的变系数Boussinesq方程: utt {αuxxx [β f(x)]ux ωuux g(x)u}x=0的Plainleve性质及相似解,其中f(x)和g(x)是两个实函数．通过对方程进行标准的WTS检验,得到了方程可积的必要条件,即方程具有Painleve性质的条件;应用CK直接方法对方程进行了相似约化,得到了原方程的五组相似变换和相似解;用这些相似解可进一步求得方程的精确解析解．