Luby and Rackoff idealized DES by replacing each round function with one large random function. In this paper, the author idealizes Camellia by replacing each S-box with one small random function, which is named Camel...Luby and Rackoff idealized DES by replacing each round function with one large random function. In this paper, the author idealizes Camellia by replacing each S-box with one small random function, which is named Camellialike scheme. It is then proved that five-round Camellia-like scheme is pseudorandom and eight-round Camellia-like scheme is super-pseudorandom for adaptive adversaries. Further the paper considers more efficient construction of Camellia-like scheme, and discusses how to construct pseudorandom Camellia-like scheme from less random functions.展开更多
Two new families of finite binary sequences are constructed using multiplicative inverse. The sequences are shown to have strong pseudorandom properties by using some estimates of certain exponential sums over finite ...Two new families of finite binary sequences are constructed using multiplicative inverse. The sequences are shown to have strong pseudorandom properties by using some estimates of certain exponential sums over finite fields. The constructions can be implemented fast since multiplicative inverse over finite fields can be computed in polynomial time.展开更多
We determined the linear complexity of a family of p2-periodic binary threshold sequences and a family of p2-periodic binary sequences constructed using the Legendre symbol,both of which are derived from Fermat quotie...We determined the linear complexity of a family of p2-periodic binary threshold sequences and a family of p2-periodic binary sequences constructed using the Legendre symbol,both of which are derived from Fermat quotients modulo an odd prime p.If 2 is a primitive element modulo p2,the linear complexity equals to p2-p or p2-1,which is very close to the period and it is large enough for cryptographic purpose.展开更多
In order to protect copyright of digital images,a new robust digital image watermarking algorithm based on chaotic system and QR factorization was proposed.The host images were firstly divided into blocks with same si...In order to protect copyright of digital images,a new robust digital image watermarking algorithm based on chaotic system and QR factorization was proposed.The host images were firstly divided into blocks with same size,then QR factorization was performed on each block.Pseudorandom circular chain(PCC) generated by logistic mapping(LM) was applied to select the embedding blocks for enhancing the security of the scheme.The first column coefficients in Q matrix of chosen blocks were modified to embed watermarks without causing noticeable artifacts.Watermark extraction procedure was performed without the original cover image.The experimental results demonstrate that the watermarked images have good visual quality and this scheme is better than the existing techniques,especially when the image is attacked by cropping,noise pollution and so on.Analysis and discussion on robustness and security issues were also presented.展开更多
Invisible watermarking methods have been applied in frequency domains, trying to embed a small image inside a large original image. The original bitmap image will be converted into frequency domain to obtain the discr...Invisible watermarking methods have been applied in frequency domains, trying to embed a small image inside a large original image. The original bitmap image will be converted into frequency domain to obtain the discrete cosine transform （DCT） matrices from its blocks. The bits of the logo image are embedded in random color components of the original image, as well as in random positions in each selected block. These positions are alternating current （AC） coefficients of the DCT matrix. The randomness is obtained from RC4 pseudorandom bit generator that determines in which color component this logo image bits will be embedded. The embedded bits have been hidden in random blocks in the image, which are chosen according to a （semi-random） function proposed in this work.展开更多
Existing solutions for secure network coding either bring significant bandwidth overhead or incur a high computational complexity. For exploiting low-overhead mechanism for secure network coding against wiretapping, t...Existing solutions for secure network coding either bring significant bandwidth overhead or incur a high computational complexity. For exploiting low-overhead mechanism for secure network coding against wiretapping, three efficient schemes are proposed for the applications with different security requirements. The basic idea behind this paper is first to encrypt a small part of source vectors and then subject the remaining original source vectors and the encrypted vectors to a special linear transformation. Also, a lightweight version of this scheme is then presented for resource-constrained networks. Moreover, an extensive scheme with enhanced security is also considered. All proposals are shown to have properties of lower security complexity and smaller bandwidth usage compared with the existing solutions. Also, the proposals can be easy to achieve flexible levels of security for various applications.展开更多
When chaotic systems are implemented on finite precision machines, it will lead to the problem of dynamical degradation. Aiming at this problem, most previous related works have been proposed to improve the dynamical ...When chaotic systems are implemented on finite precision machines, it will lead to the problem of dynamical degradation. Aiming at this problem, most previous related works have been proposed to improve the dynamical degradation of low-dimensional chaotic maps. This paper presents a novel method to construct high-dimensional digital chaotic systems in the domain of finite computing precision. The model is proposed by coupling a high-dimensional digital system with a continuous chaotic system. A rigorous proof is given that the controlled digital system is chaotic in the sense of Devaney's definition of chaos. Numerical experimental results for different high-dimensional digital systems indicate that the proposed method can overcome the degradation problem and construct high-dimensional digital chaos with complicated dynamical properties. Based on the construction method, a kind of pseudorandom number generator (PRNG) is also proposed as an application.展开更多
Let S be a family of binary sequences constructed from interleaved construction. The linear spans of binary sequences in S are studied in this paper. In order to achieve the largest linear span, a criterion is present...Let S be a family of binary sequences constructed from interleaved construction. The linear spans of binary sequences in S are studied in this paper. In order to achieve the largest linear span, a criterion is presented for the base sequences with periodp, where p is a prime and 2 is a primitive root modulop2. It is shown that any sequence in S has the largest linear span under the criterion. Moreover, such base sequences can be chosen easily.展开更多
The chaos-based feedforward output functions for combining keystream generators are proposed according to chaotic dynamic theory. The generated binary signals are independently and identically distributed, and have pr...The chaos-based feedforward output functions for combining keystream generators are proposed according to chaotic dynamic theory. The generated binary signals are independently and identically distributed, and have predictable periods. All experiments correspond to the theoretical prediction very well.展开更多
We design a practical and provablysecure block ciper over small domain and non-binary inputs,which is also can be considered as a pseudorandom permutation on N elements.Our work is based on a relation we found between...We design a practical and provablysecure block ciper over small domain and non-binary inputs,which is also can be considered as a pseudorandom permutation on N elements.Our work is based on a relation we found between the small domain ciper and the negative hypergeometric probability(NHG) distribution.We prove that our block ciper achieves ideal security,that is,it is indistinguishable from a random permutation even if the adversary had already observed N plaintext-cipertext pairs.In particular,we initiate an efficient and sufficiently precise sampling algorithm for negative hypergeometric distribution.展开更多
We present a method for constructing k-ary sequences over elliptic curves. Using the multiplicative character of order k of finite fields, we construct a family of k-ary pseudorandom elliptic curve sequences. The pseu...We present a method for constructing k-ary sequences over elliptic curves. Using the multiplicative character of order k of finite fields, we construct a family of k-ary pseudorandom elliptic curve sequences. The pseudorandom measures, such as the well-distribution measure, the correlation measure of order e, and the linear complexity are estimated by using certain character sums. Such sequences share the same order of magnitude on the well-distribution measure, the correlation measure of order e as the ＇truly＇ random sequences. The method indicates that it is possible to construct ＇good＇ pseudorandom sequences over elliptic curves widely used in public key cryptography.展开更多
A chaotic system with various equilibrium types has rich dynamic behaviors.Its state can switch flexibly among different families of attractors,which is beneficial to the practical applications.So it has been widely c...A chaotic system with various equilibrium types has rich dynamic behaviors.Its state can switch flexibly among different families of attractors,which is beneficial to the practical applications.So it has been widely concerned in recent years.In this paper,a new 5D hyper-chaotic system is proposed.The important characteristic of the system is that it may have multiple types of equilibrium points by changing system parameters,namely,linear equilibrium point,no equilibrium point,non-hyperbolic unstable equilibrium point and stable hyperbolictype equilibrium point.Furthermore,there are hyper-chaotic phenomena and multi-stability about the coexistence of multiple chaotic attractors and the coexistence of hyper-chaotic attractors and chaotic attractors in the system.In addition,the system,complexity is analyzed.It is found that the complexity is close to 1 in the hyper-chaotic state and a pseudo-random sequence generated by the system passes all the statistical tests.Finally,an analog circuit of the system is designed and simulated.展开更多
The standard method to construct a finite field requires a primitive irreducible polynomial of a given degree. Therefore, it is difficult to apply for the construction of huge finite fields. To avoid this problem, we ...The standard method to construct a finite field requires a primitive irreducible polynomial of a given degree. Therefore, it is difficult to apply for the construction of huge finite fields. To avoid this problem, we propose a new method to construct huge finite fields with the characteristic p = 5 by using an Artin-Schreier tower. Utilizing the recursive basis of the Artin-Schreier tower, we define a nmltiplication algorithm The algorithm can explicitly calculate the multiplication of two elements on the top finite field of this tower, without any primitive element. We also define a linear recurrence equation as an application, which produces a sequence of numbers, and call the new pseudorandom number generator Abstract Syntax Tree （AST） for p = 5. The experircental results show that our new pseudorandom number generator can produce a sequence of numbers with a long period.展开更多
In recent years, various chaotic equation based pseudorandom number generators have been proposed. However, the chaotic equations are all defined in the real number field. In this paper, an equation is proposed and pr...In recent years, various chaotic equation based pseudorandom number generators have been proposed. However, the chaotic equations are all defined in the real number field. In this paper, an equation is proposed and proved to be chaotic in the imaginary axis. And a pseudorandom number generator is constructed based on the chaotic equation. The alteration of the definitional domain of the chaotic equation from the real number field to the complex one provides a new approach to the construction of chaotic equations, and a new method to generate pseudorandorn number sequences accordingly. Both theoretical analysis and experimental results show that the sequences generated by the proposed pseudorandom number generator possess many good properties.展开更多
This paper presents a fast pseudorandom generation algorithm,which is based on the BLAKE hash function and can pass the random test of the NIST(National Institute of Standards and Technology)Statistical Test Suite.Thr...This paper presents a fast pseudorandom generation algorithm,which is based on the BLAKE hash function and can pass the random test of the NIST(National Institute of Standards and Technology)Statistical Test Suite.Through theoretical analysis and experimental imitation,our new algorithm is proven to be more secure and efficient than G-SHA1.Simultaneously,we introduce and discuss the BLAKE in detail.Its security shows that can be utilized to generate pseudorandom bit sequences,which the experimental results show the BLAKE hash function has excellent pseudorandomness.Therefore,we believe the BLAKE is one of the most potential candidate algorithms of SHA-3 program.展开更多
Under Kerckhoff principle,this paper discusses the security property of an image encryp-tion scheme with a pseudorandom permutation.Some findings on the security problems of the algo-rithm are reported in the followin...Under Kerckhoff principle,this paper discusses the security property of an image encryp-tion scheme with a pseudorandom permutation.Some findings on the security problems of the algo-rithm are reported in the following:(1) If each row or column of the plain-image matrix is the same,the receiver cannot decrypt correctly.(2) Each plain-text word is correlated with single cipher-text word,but independent of other cipher-text word,which cannot meet the principles of algorithm design-diffusion and confusion.(3) If the cycle numbers are relatively small,statistics attack can be used to reveal some visual information of any other plain-images encrypted with the same secret key.Con-sidering the above problems,we propose an improved algorithm and then analyze its performance.Theoretical analysis and simulation results show that the improved algorithm can obtain better cryptographic properties,such as statistical characteristics,difference characteristics,and so on.展开更多
A novel magnetic grating based on calibration was proposed.Two tracks,look-up track and index track,were used to realize absolute output.Magnets of look-up track were magnetized according to N-S-N-S,and magnetic field...A novel magnetic grating based on calibration was proposed.Two tracks,look-up track and index track,were used to realize absolute output.Magnets of look-up track were magnetized according to N-S-N-S,and magnetic field was sensed by 6 linear Hall sensors.Three signals whose phase shift is 120° were obtained through difference,and the offset of magnetic head in a signal period could be obtained by look-up table;Magnets of index track were magnetized according to pseudorandom binary sequence.Hall sensors were used to get the absolute offset of the signal period to which the magnetic head is belonged.The magnetic grating was calibrated using a higher resolution optical grating:output of optical grating and signals from magnetic grating were sampled at the same time and transmitted to computer,the relation between them could be got and stored in MCU for looking-up.The displacement was got according to Hall signals while in working state.A magnetic grating prototype was made,and it could realize absolute detecting in 2048 mm and the resolution could achieve to 0.001 mm.Its structure is simple,cost is very low and it is suitable for mass production.展开更多
In this paper, the autocorrelations of maximal period Feedback with Carry Shift Register sequences （l-sequences） are discussed. For an l-sequence a with connection integer q = p^e（e ≥ 2） and period T = p^t-1（p- ...In this paper, the autocorrelations of maximal period Feedback with Carry Shift Register sequences （l-sequences） are discussed. For an l-sequence a with connection integer q = p^e（e ≥ 2） and period T = p^t-1（p- 1）, and for any integer i, 1 ≤ i ≤ e/2, by calculating the number of certain sets, it is shown that the autocorrelation of a with shift τ= kT/2p^i is Ca（τ） =（-1）^k-1 T/p^2i-1, where 1 ≤ k ≤ 2p^i - 1, and gcd（k,2p^i） = 1. This result shows there do exist some shifts such that the autocorrelations of l-sequences are high although most autocorrelations are low. Such result also holds for the decimations of l-sequences.展开更多
This paper proposes an efficient, high-tech method of construction of pseudorandom binary sequences generators with a repetition period 2n?for n-bit shift register with a nonlinear feedback function. The developed met...This paper proposes an efficient, high-tech method of construction of pseudorandom binary sequences generators with a repetition period 2n?for n-bit shift register with a nonlinear feedback function. The developed method is illustrated by constructing a nonlinear function feedback shift register. It is proved that the offered method requires the realization of a memory size proportional to n2?that allows making successful use of suitable generators for practical use on the shift register of the longer word.展开更多
基金Supported partially by the National Natural Science Foundation of China under Grants No, 60373047 and No, 90304007 the National Basic Research 973 Program of China under Grant No. 2004CB318004 the National High-Technology Development 863 Program of China under Grant No. 2003AA144030.
文摘Luby and Rackoff idealized DES by replacing each round function with one large random function. In this paper, the author idealizes Camellia by replacing each S-box with one small random function, which is named Camellialike scheme. It is then proved that five-round Camellia-like scheme is pseudorandom and eight-round Camellia-like scheme is super-pseudorandom for adaptive adversaries. Further the paper considers more efficient construction of Camellia-like scheme, and discusses how to construct pseudorandom Camellia-like scheme from less random functions.
文摘近日,西安电子科技大学数学与交叉科学研究院菁英副教授李哲与上海交通大学教授邢朝平、博士研究生姚逸洲和副教授袁晨合作,在伪随机关联生成器(Pseudorandom Correlation Generator,PCG)方面取得重要进展,相关论文“Efficient Pseudorandom Correlation Generators for Any Finite Field”被EUROCRYPT(欧密会)2025录用发表。
基金Supported by the Open Funds of Key Lab of Fujian Province University Network Security and Cryptology (07B005)the Funds of the Education Department of Fujian Province (JA07164)the Natural Science Foundation of Fujian Province of China (2007F3086)
文摘Two new families of finite binary sequences are constructed using multiplicative inverse. The sequences are shown to have strong pseudorandom properties by using some estimates of certain exponential sums over finite fields. The constructions can be implemented fast since multiplicative inverse over finite fields can be computed in polynomial time.
基金the National Natural Science Foundation of China，the Open Funds of State Key Laboratory of Information Security (Chinese Academy of Sciences)，the Program for New Century Excellent Talents in Fujian Province University
文摘We determined the linear complexity of a family of p2-periodic binary threshold sequences and a family of p2-periodic binary sequences constructed using the Legendre symbol,both of which are derived from Fermat quotients modulo an odd prime p.If 2 is a primitive element modulo p2,the linear complexity equals to p2-p or p2-1,which is very close to the period and it is large enough for cryptographic purpose.
基金Project(2007AA01Z241-2) supported by the National High-tech Research and Development Program of ChinaProject(2006XM002) supported by Beijing Jiaotong University Science Foundation,ChinaProject(0910KYZY55) supported by the Fundamental Research Funds for the Central University in China
文摘In order to protect copyright of digital images,a new robust digital image watermarking algorithm based on chaotic system and QR factorization was proposed.The host images were firstly divided into blocks with same size,then QR factorization was performed on each block.Pseudorandom circular chain(PCC) generated by logistic mapping(LM) was applied to select the embedding blocks for enhancing the security of the scheme.The first column coefficients in Q matrix of chosen blocks were modified to embed watermarks without causing noticeable artifacts.Watermark extraction procedure was performed without the original cover image.The experimental results demonstrate that the watermarked images have good visual quality and this scheme is better than the existing techniques,especially when the image is attacked by cropping,noise pollution and so on.Analysis and discussion on robustness and security issues were also presented.
基金supported by the Deanship of Research and Graduate Studies at Applied Science University, Amman, Jordan
文摘Invisible watermarking methods have been applied in frequency domains, trying to embed a small image inside a large original image. The original bitmap image will be converted into frequency domain to obtain the discrete cosine transform （DCT） matrices from its blocks. The bits of the logo image are embedded in random color components of the original image, as well as in random positions in each selected block. These positions are alternating current （AC） coefficients of the DCT matrix. The randomness is obtained from RC4 pseudorandom bit generator that determines in which color component this logo image bits will be embedded. The embedded bits have been hidden in random blocks in the image, which are chosen according to a （semi-random） function proposed in this work.
基金Supported by the National Natural Science Foundation of China(6127117)
文摘Existing solutions for secure network coding either bring significant bandwidth overhead or incur a high computational complexity. For exploiting low-overhead mechanism for secure network coding against wiretapping, three efficient schemes are proposed for the applications with different security requirements. The basic idea behind this paper is first to encrypt a small part of source vectors and then subject the remaining original source vectors and the encrypted vectors to a special linear transformation. Also, a lightweight version of this scheme is then presented for resource-constrained networks. Moreover, an extensive scheme with enhanced security is also considered. All proposals are shown to have properties of lower security complexity and smaller bandwidth usage compared with the existing solutions. Also, the proposals can be easy to achieve flexible levels of security for various applications.
基金Project supported by the National Key R&D Program of China(Grant No.2017YFB0802000)the Cryptography Theoretical Research of National Cryptography Development Fund,China(Grant No.MMJJ20170109).
文摘When chaotic systems are implemented on finite precision machines, it will lead to the problem of dynamical degradation. Aiming at this problem, most previous related works have been proposed to improve the dynamical degradation of low-dimensional chaotic maps. This paper presents a novel method to construct high-dimensional digital chaotic systems in the domain of finite computing precision. The model is proposed by coupling a high-dimensional digital system with a continuous chaotic system. A rigorous proof is given that the controlled digital system is chaotic in the sense of Devaney's definition of chaos. Numerical experimental results for different high-dimensional digital systems indicate that the proposed method can overcome the degradation problem and construct high-dimensional digital chaos with complicated dynamical properties. Based on the construction method, a kind of pseudorandom number generator (PRNG) is also proposed as an application.
基金Supported by the National Natural Science Foundation ofChina (60573053 , 60603012)the Specialized Research Fund for the Doctoral Program of Higher Education of China (20050512002)
文摘Let S be a family of binary sequences constructed from interleaved construction. The linear spans of binary sequences in S are studied in this paper. In order to achieve the largest linear span, a criterion is presented for the base sequences with periodp, where p is a prime and 2 is a primitive root modulop2. It is shown that any sequence in S has the largest linear span under the criterion. Moreover, such base sequences can be chosen easily.
文摘The chaos-based feedforward output functions for combining keystream generators are proposed according to chaotic dynamic theory. The generated binary signals are independently and identically distributed, and have predictable periods. All experiments correspond to the theoretical prediction very well.
基金National 973 Fundamental Basic Research Program under grant No.2014CB340600 and by the National Natural Science Foundations of China
文摘We design a practical and provablysecure block ciper over small domain and non-binary inputs,which is also can be considered as a pseudorandom permutation on N elements.Our work is based on a relation we found between the small domain ciper and the negative hypergeometric probability(NHG) distribution.We prove that our block ciper achieves ideal security,that is,it is indistinguishable from a random permutation even if the adversary had already observed N plaintext-cipertext pairs.In particular,we initiate an efficient and sufficiently precise sampling algorithm for negative hypergeometric distribution.
基金Supported by the National Natural Science Foundation of China (61063041)the Program for New Century Excellent Talents in Fujian Province University (JK2010047)the Open Funds of State Key Laboratory of Information Security (01-01-1)
文摘We present a method for constructing k-ary sequences over elliptic curves. Using the multiplicative character of order k of finite fields, we construct a family of k-ary pseudorandom elliptic curve sequences. The pseudorandom measures, such as the well-distribution measure, the correlation measure of order e, and the linear complexity are estimated by using certain character sums. Such sequences share the same order of magnitude on the well-distribution measure, the correlation measure of order e as the ＇truly＇ random sequences. The method indicates that it is possible to construct ＇good＇ pseudorandom sequences over elliptic curves widely used in public key cryptography.
基金the Science Foundation of Ministry of Education of China(No.02152)。
文摘A chaotic system with various equilibrium types has rich dynamic behaviors.Its state can switch flexibly among different families of attractors,which is beneficial to the practical applications.So it has been widely concerned in recent years.In this paper,a new 5D hyper-chaotic system is proposed.The important characteristic of the system is that it may have multiple types of equilibrium points by changing system parameters,namely,linear equilibrium point,no equilibrium point,non-hyperbolic unstable equilibrium point and stable hyperbolictype equilibrium point.Furthermore,there are hyper-chaotic phenomena and multi-stability about the coexistence of multiple chaotic attractors and the coexistence of hyper-chaotic attractors and chaotic attractors in the system.In addition,the system,complexity is analyzed.It is found that the complexity is close to 1 in the hyper-chaotic state and a pseudo-random sequence generated by the system passes all the statistical tests.Finally,an analog circuit of the system is designed and simulated.
基金supported by Overseas Scholars Research Fund of Heilongjiang Provinicial Education Department
文摘The standard method to construct a finite field requires a primitive irreducible polynomial of a given degree. Therefore, it is difficult to apply for the construction of huge finite fields. To avoid this problem, we propose a new method to construct huge finite fields with the characteristic p = 5 by using an Artin-Schreier tower. Utilizing the recursive basis of the Artin-Schreier tower, we define a nmltiplication algorithm The algorithm can explicitly calculate the multiplication of two elements on the top finite field of this tower, without any primitive element. We also define a linear recurrence equation as an application, which produces a sequence of numbers, and call the new pseudorandom number generator Abstract Syntax Tree （AST） for p = 5. The experircental results show that our new pseudorandom number generator can produce a sequence of numbers with a long period.
基金Project supported by the National Natural Science Foundation of China (Grant No. 60973162)the Natural Science Foundation of Shandong Province, China (Grant No. ZR2009GM037)+1 种基金the Science and Technology of Shandong Province, China(Grant No. 2010GGX10132)the Key Program of the Natural Science Foundation of Shandong Province, China (Grant No. Z2006G01)
文摘In recent years, various chaotic equation based pseudorandom number generators have been proposed. However, the chaotic equations are all defined in the real number field. In this paper, an equation is proposed and proved to be chaotic in the imaginary axis. And a pseudorandom number generator is constructed based on the chaotic equation. The alteration of the definitional domain of the chaotic equation from the real number field to the complex one provides a new approach to the construction of chaotic equations, and a new method to generate pseudorandorn number sequences accordingly. Both theoretical analysis and experimental results show that the sequences generated by the proposed pseudorandom number generator possess many good properties.
基金Supported by the National High Technology Research and Development Program of China (863 Program) ( 2007AA01Z411)the National Natural Science Foundation of China ( 60673071, 60970115 )
文摘This paper presents a fast pseudorandom generation algorithm,which is based on the BLAKE hash function and can pass the random test of the NIST(National Institute of Standards and Technology)Statistical Test Suite.Through theoretical analysis and experimental imitation,our new algorithm is proven to be more secure and efficient than G-SHA1.Simultaneously,we introduce and discuss the BLAKE in detail.Its security shows that can be utilized to generate pseudorandom bit sequences,which the experimental results show the BLAKE hash function has excellent pseudorandomness.Therefore,we believe the BLAKE is one of the most potential candidate algorithms of SHA-3 program.
基金Supported by the National Natural Science Foundation of China (No. 60874091)the Six Projects Sponsoring Talent Summits of Jiangsu Province (No. SJ209006)+2 种基金the Foundation for Doctoral Program of High Education of China(No. 20103223110003)the Natural Science Foundation of Jiangsu Province (No. 08KJD510022)the Post-graduate Scientific Innovation Project for Universities of Jiangsu Province (No. CXZZ11-0401)
文摘Under Kerckhoff principle,this paper discusses the security property of an image encryp-tion scheme with a pseudorandom permutation.Some findings on the security problems of the algo-rithm are reported in the following:(1) If each row or column of the plain-image matrix is the same,the receiver cannot decrypt correctly.(2) Each plain-text word is correlated with single cipher-text word,but independent of other cipher-text word,which cannot meet the principles of algorithm design-diffusion and confusion.(3) If the cycle numbers are relatively small,statistics attack can be used to reveal some visual information of any other plain-images encrypted with the same secret key.Con-sidering the above problems,we propose an improved algorithm and then analyze its performance.Theoretical analysis and simulation results show that the improved algorithm can obtain better cryptographic properties,such as statistical characteristics,difference characteristics,and so on.
基金Sponsored by the Scientific Research Foundation of Heilongjiang Province for Returned Chinese Scholars(Grant No. 2006212)
文摘A novel magnetic grating based on calibration was proposed.Two tracks,look-up track and index track,were used to realize absolute output.Magnets of look-up track were magnetized according to N-S-N-S,and magnetic field was sensed by 6 linear Hall sensors.Three signals whose phase shift is 120° were obtained through difference,and the offset of magnetic head in a signal period could be obtained by look-up table;Magnets of index track were magnetized according to pseudorandom binary sequence.Hall sensors were used to get the absolute offset of the signal period to which the magnetic head is belonged.The magnetic grating was calibrated using a higher resolution optical grating:output of optical grating and signals from magnetic grating were sampled at the same time and transmitted to computer,the relation between them could be got and stored in MCU for looking-up.The displacement was got according to Hall signals while in working state.A magnetic grating prototype was made,and it could realize absolute detecting in 2048 mm and the resolution could achieve to 0.001 mm.Its structure is simple,cost is very low and it is suitable for mass production.
基金the 863 Project of China (No.2006AA01Z417) the National Natural Science Foundation of China (No.60673081).
文摘In this paper, the autocorrelations of maximal period Feedback with Carry Shift Register sequences （l-sequences） are discussed. For an l-sequence a with connection integer q = p^e（e ≥ 2） and period T = p^t-1（p- 1）, and for any integer i, 1 ≤ i ≤ e/2, by calculating the number of certain sets, it is shown that the autocorrelation of a with shift τ= kT/2p^i is Ca（τ） =（-1）^k-1 T/p^2i-1, where 1 ≤ k ≤ 2p^i - 1, and gcd（k,2p^i） = 1. This result shows there do exist some shifts such that the autocorrelations of l-sequences are high although most autocorrelations are low. Such result also holds for the decimations of l-sequences.
文摘This paper proposes an efficient, high-tech method of construction of pseudorandom binary sequences generators with a repetition period 2n?for n-bit shift register with a nonlinear feedback function. The developed method is illustrated by constructing a nonlinear function feedback shift register. It is proved that the offered method requires the realization of a memory size proportional to n2?that allows making successful use of suitable generators for practical use on the shift register of the longer word.
