Abstract:The mathematical security of the RSA cryptosystem is based on the problem of factoring large integers. At present, the number field sieve is the most efficient algorithm known for factoring integers larger than 365 bits, while its time complexity is still sub-exponential. Integers larger than 1024 bits, which are widely used in RSA cryptosystem, cannot be factored by means of the number field sieve. So it is significant to study the number field sieve.Now, the general number field sieve often uses two number fields, while multiple number fields are seldom considered. The general number field sieve, through adaptation, can use three number fields, i.e. two algebraic number fields and one rational number field. Analysis shows that the time complexity of the modified number field sieve and the general number field sieve are at the same level. However, the modified number field sieve can combine more computation, so it can save more time in practice. Finally, the result is verified by two experiments.

Abstract:Dual system encryption was first proposed by Waters as a powerful method to prove full security for identity-based encryption (IBE) schemes and its extensions. To construct fully secure schemes, the application of dual system encryption is considered and a generic construction of fully secure schemes is presented. The construction combines a dual system encryption IBE scheme with a normal secure scheme and produces a new scheme which can be proven secure by dual system encryption. Based on the proposed generic construction, an instantiation, which is a hierarchical identity-based encryption (HIBE) scheme with constant ciphertext size, is presented. This scheme is more efficient than Waters’ original dual system encryption HIBE scheme, and it is proven fully secure under the Decision BDH and Decision Linear assumptions.

Abstract:Drawing on the idea of the quantum secure direct communication (QSDC), a novel quantum dialogue scheme based on Bell states is presented in this paper. The proposed scheme can realize authorized parties’ secure exchange of their respective secret messages simultaneously only through one communication. In this scheme, a random bit string and checking particles are used to ensure the security; the scheme is secure against eavesdropper's commonly used attacks, such as intercept/resend attack, Trojan horse attack and entanglement attack. A serious problem called “information leakage” or “classical correlation” is found in some quantum dialogue protocols, namely, any eavesdropper can elicit some information about the secret from the classical communication of the legal users. Fortunately, our protocol can discard the drawback “information leakage”. In addition, our protocol possesses high efficiency 66.7% and is feasible. Finally, the protocol is applied to the scheme based on two-qutrit entangled states with a secure communication.

Abstract:The Algebraic Normal Form (ANF) of a Boolean function is unique, which is very important in the research of Boolean function. The 128 ANFs of the component functions of the round transformation (the composition of Sbox, ShiftRow and MixColumn)of the Advanced Encryption Standard(AES) were obtained by using the Mathematica software. Each component function is a 32-variable Boolean function. The number of terms is between 448 and 545, and the average number is 496, which is much smaller than 2³¹, the number of terms of a random 32-variable Boolean function. This shows a great deviation of the AES round transformation with a random permutation. The time complexity of getting the 128 ANFs of the AES round transformation is only a few minutes on a PC with a 2GHz CPU. The method is better than the classical one in computing the ANF from truth table, with total time complexity of obtaining the 128 ANFs O(128×32×2³²) = O(2⁴⁴). As an application, an equation system for 1-full round of AES was obtained by using the ANFs. The equation system was solved by using Cryptominisat 2.9.0. By the method of Guess-and-Determine, the 128 bits of keys can be recovered in less than 2³³hours on a PC with one known plaintext.

Abstract:In 2009, based on a combinatorial conjecture, Tu and Deng constructed a class of Boolean functions in even variables with optimal algebraic immunity, optimal algebraic degree and good nonlinearity. This class of functions is called the Tu-Deng function. Based on the same conjecture, they also proposed a class of resilient functions in even variables with suboptimal algebraic immunity, optimal algebraic degree and good nonlinearity. By studying the cryptographic properties of the concatenation of two Boolean functions derived from the Tu-Deng function, based on Tu-Deng's conjecture, a class of resilient Boolean functions in odd variables is proposed. This class of functions has suboptimal algebraic immunity, optimal algebraic degree and good nonlinearity.

Abstract:The formulas of binary Edwards curves which can be halved are transformed from the doubling ones by using the symmetry of the formulas. Two situations are to be handled in the derivation by the parameters of the curves. In the case of d₁≠d₂, it is naturally to get a halving algorithm by using the relation of birational equivalence from the Weierstrass curves, the trace functions and the half-trace functions. In the case of d₁＝d₂, a theorem is given to prove it. It is not easy to get a halving algorithm, although the doubling formulas are simpler in this case. Then the efficiency of the halving algorithm is analyzed. The result shows that the efficiency of the halving algorithm cannot catch up with that of the doubling one. Using the ω-coordinate, the halving algorithm is simplified, and is further used to compute the scalar multiplication.

Abstract:In order to obtain a fast multiplication on elliptic curves, the Gallant-Lambert-Vanstone(GLV) method is introduced to the general situation in dimension 4, one of the open problems in Galbraith, Lin and Scott's work(J. Cryptol. DOI: 10.1007/s00145-010-9065-y) is answered, that is, studying the performance of 4-dimensional GLV method for faster point multiplication on some GLS curves over Fp² with j-invariant 1728. Finally some results and examples are presented, showing that the 4-dimensional GLV method runs in between 70% and 73% the time of the 2-dimensional GLV method which Galbraith et al. did in their work.

Abstract:The key schedule algorithm plays a crucial role in the block cipher, thus many attacks pay more attention to it at present. Through analyzing the non-linear function FI and the key schedule algorithm of MISTY1, and observing the distribution of subkeys as well, a weak-key class of MISTY1 was found, which encompasses 2⁹⁰weak keys that are vulnerable to related-key amplified boomerang attack. Based on the weak-key class, two related-key differential characteristics were found. Then, the research presented a 7-round related-key amplified boomerang distinguisher of MISTY1, which can accomplish an attack on the 8-round MISTY1 without the last FL lay. The attack requires 2⁶³chosen plaintexts, and the time complexity of the attack is 2⁷⁰. The attack is the first attack on MISTY1 without the last FL lay. Besides, compared with the similar attacks, the limit of the related-key of our attack is released.

Abstract:Algebraic Immunity has been considered as one of significant cryptographic properties for Boolean functions. In order to resist algebraic attack, high algebraic immunity is necessary for those Boolean functions used in symmetric cipher algorithms. Based on “orbit exchange” technique, this research presents a construction of rotation symmetric Boolean functions with the maximum algebraic immunity on even number of variables. These functions have strong resistance against algebraic attacks. These functions also have much better nonlinearity and optimal algebraic degree.

Abstract:The study of permutation polynomials over finite fields has been a hotspot research topic for a long time. In fact, it is equivalent to the study of one-to-one mapping between finite fields. Therefore, it has many important applications in coding theory, cryptography and algebraic curves, etc. Carlitz had a characterization of permutation polynomials. He proved that if f(x)is a polynomial with coefficients over finite field Fq satisfyingf(0)=f(1) and η(f(a)-f(b)=η(a-b)for every a,b∈Fq, where η is the quadratic character of Fq* . Then f(x)=x^pjfor some integer. In this note, we proved that the above result is also true for any multiplicative character of Fq*.

Abstract:Addition modulo 2ⁿand XOR addition are two code links which are often used in cipher algorithms, the consistent degree of the two links means the difference degree when the computing sequence is changed in the equation including the two links. The difference function between addition modulo 2ⁿ and XOR addition corresponding to associative law is studied. When the computing sequence of ［(x⊕y)+z］mod 2ⁿ is changed, the computation formulae of the probability distribution of the difference function ξ(x,y,z)=［(x⊕y)+_n^z］⊕［x⊕(y+_n^z)］ is given, and the square sum of the probability is given too. The results presented are useful for some distinguishing attack.

Abstract:Linear transformation with good branch number plays a significant role in designing components of symmetric key primitives. Linear transformation based on XOR of several rotations can be efficiently implemented, and has been widely used in the block ciphers such as SMS4, HIGHT and the hash functions SHA-2, MD6. Besides, if the linear transformation is involutional, it will facilitate the decryption process. In view of this, a kind of involutional linear transformation based on the XOR of several rotations was studied, the numeration of this kind of linear transformation was given and the branch number was shown to be upper bounded by 4. Meanwhile, the relationship between the parameters of the rotations and the branch number was discussed, which provides a theoretical basis for the design. 

Abstract:Spread spectrum technology has been widely used in the field of communication and satellite navigation. Traditional methods to generate simulation data have heavy computation burden, ignoring the channel factors and other issues. Considering characteristics of spread spectrum systems signals and noise, a fast and efficient method is presented to generate signals based on spreading code chip and band-limited Gaussian noise based on AR model. Compared with the conventional high-precision methods, the complexity of calculation decreased from 1GHz rate to chip rate, and maintained the flexibility of signal generation and channel factors control at the same time. This research can be used in the simulation of modern GNSS receivers.

Abstract:Inbound user capacity is an important specification of RDSS system design, which is mainly limited by the inbound signal multiple access interference. To improve the spreading code rate can increase the corresponding inbound capacity. However, the satellite transponder bandwidth limits the maximum spreading code rate, which limits the maximum capacity of inbound signals with a single spread spectrum. As the satellite transponder bandwidth is limited, a spread spectrum separation method was proposed to increase inbound capacity. The situation of separating the spread spectrum into two and three was analyzed respectively. thus obtaining the optimal value of spreading code rate in the both cases. Simulation results show that the existing transponder bandwidth separated into two spreading spectrums can increase inbound capacity 29%, the spectrums which separated in to can increase inbound capacity 37%.

Abstract:Aiming at solving the real-time computation of the satellite orbit in GNSS (Global Navigation Satellite System) emulator with multiple constellations, the Newton and Hermite polynomial interpolation algorithms were analyzed and compared by computing efficiency and accuracy. The precision of the satellite position and velocity (PV) performed better by adding “window” in the Newton algorithm. The computation examples show that the real-time and high-precision computation of the satellite PV is achieved with position at the equation interval epoch known and velocity unknown. The results also show that the new method speeds up the computation seven times faster than the direct ephemeris calculation, and yeilds better performance in orbit precision than the 3-order Hermite Interpolation, for the position error is less than millimeter and the velocity error 1e-5 m/s.

Abstract:Code Correlation Reference Waveform has been the research hotspot for its flexibility and outstanding multipath mitigation performance in GNSS receivers. But the analysis from the literature related usually assumes that the single-side bandwidth is infinite or much larger than the chipping rate and only specified waveform has been studied, thus there is a lack of quantitative results for modern band-limited receivers. Based on the CCRW principle, the formulae and design constraints for the discriminator curve of any reference waveform were derived. The multi-path error envelopes of quasi- coherent W2/W4/W5 waveforms were studied. Simulation results indicate that W4/W5 outperforms the W2 algorithm. A QPSK (10) prototype receiver developed for GPS L5 and Galileo E5a/E5b was tested with a GNSS simulator. Compared with Narrow Correlator, the multipath envelope area for a 3dB attenuated multipath signal has been improved by 63% and 72% for W2 and W5 respectively. This research can be used as a guideline for modern GNSS receivers.

Abstract:In the typical urban environment, GPS standalone can hardly satisfy the requirement of continuous positioning, particularly in the weak signal or no signal environment. Fortunately, this problem can be solved by using the integration method based on GPS and non-LOS (Line of Sight) positioning such as RFID positioning. To solve the problem of computational load in the traditional GPS/RFID integration based on all selection of RFID observations, this research proposed an optimal selection method of RFID observations with the minimum positioning error under the weighted observation condition. The experiment results show that the geometric distribution of precision in the environments, such as shadow or blockage, can be improved by using the proposed method, and both availability and accuracy of positioning can be improved efficiently. Moreover, the computational load can be decreased dramatically through this proposed method.

Abstract:In navigation war, the technique of satellite power-enhancement has been an important measure to improve the viability of the satellite navigation system. With regard to the problem about how to maintain the navigation capabilities of Compass system for the territory of China and the surrounding area in the context of navigation war, this researcg presents a satellite navigation system power enhancement program based on mixed constellation and guidelines of best GDOP value. Then, the effect to the performance of coverage, availability and implementation complexity in area covered by power enhancement signals under different realization types was analyzed. The results from simulation show that ‘5GEO+4MEO’ combination of power enhancement can achieve all-time coverage with the avalibility level of 100% (GDOP<6.3) for our country’s territory and coastal regions. Furthermore, this scheme also has the quality of low complexity and good stability and can be introduced as a regional power enhanced options.

Abstract:Statistical performance evaluation based on available ratio of antijam antenna array has been considered a common viewpoint for GNSS evaluation. But in some aspects, the traditional evaluation method has several deficiencies as follows: the first is the hypothesis of independent uniform distribution of signal DOA, which is not in accordance with the navigation constellation; the second is the single signal available ratio which is unable to meet the navigation requirements. Aiming at these two problems, the research extended the average available ratio of single signal to the average solution probability and navigation service availability which are associated with the navigation solution performance. Finally, the new index was validated by a simulation under the COMPASS navigation constellation.

Abstract:As the technology of the dual-mode RDSS receiver with passive and active positioning function has been developing rapidly nowadays, the high precision simulator is strongly demanded. The simulator comprises the satellite orbit module, the target trajectory calculation module, the error calculation module, and the like. The production of signal parameters has been a crucial technique that must be solved for the RDSS signal simulator. However, compared with GPS system, RDSS satellite system is a transmitting system with transponder and frequency conversion, which gives rise to more complexity in RDSS signal parameter production. Therefore, for the transmitting satellite system, signal parameter production algorithm was proposed; the formulae for the Doppler frequency shift were derived for the first time. Simulated experiments were carried out, and the results verified the validity of the algorithm.

Abstract:The routing and channel assignment (RCA) can affect the performance of wireless mesh networks (WMN) largely. In order to solve the RCA problem of WMN, a scheme called CRAG (Channel and Routing Assignment based on Game) for WMN is proposed and studied. CRAG is a kind of coordination game which models each node of the network as a player. The players strategy is the routing and channel assignment scheme related to the node. The payoff function is the successful transmission traffic given a traffic demand matrix. Player coordinately optimizes the payoff function to maximize the network throughput. Simulation results based on NS3 show that CRAG performs much better than other state-of-the-art schemes in terms of convergence, delay, loss rate and throughput. It proves that coordination game can be used to solve the RCA of WMN and improve the performance of network effectively. 

Abstract:For the problem of survive particle importance sampling in multitarget tracking Probability Hypothesis Density particle filter, a new algorithm of survive particle importance sampling is presented. For every particle, the algorithm exploits likelihood between latest measurements, and the particle chooses one measurement of the set of measurement to obtain importance distribution by update particle, and draws samples of survive particle from the importance distribution. The presented algorithm reduced degeneration of particle efficiently. In simulation scenario of 3 targets tracking, the optimal sub-pattern assignment metric of particle probability hypothesis density filter, which adopted the presented survive particle importance sample method, decreases about 70Km when targets model used in target tracking method is different from actual targets model. The proposed method enhances the robustness of multitarget tracking of particle probability hypothesis density filter remarkably.

Abstract:Integrative joint operation carries “land-sea-air-space-near space” five-in-one character. Near space has an important strategic status in the system combat based on information system, due to two advantages in information support and fast long distance delivery. Research progress of near space vehicle was summarized by considering technology factors. The key technologies and development trend of near space vehicle were analyzed. Several proposals about developing near space vehicle were provided. 

Abstract:Due to the large initial errors, uncertainties and disturbances in roll-channel of bank-to-turn hypersonic vehicle, an adaptive global integral sliding mode control approach is proposed. An adaptive parameter adjuster control rule was introduced into the sliding mode control, with the adaptive law adjusting parameter of the sliding mode controller to approximate the upper bound of parameter uncertainties and disturbances, which ensures the reachability of the sliding-mode during the whole control process. On the basis of this, an adaptive sliding mode control based on global integral sliding-mode is proposed. With this mode, the steady-state tracking error was eliminated while the system lies on the sliding-mode from beginning of any initial state. It also can avoid large overshoots due to the large initial errors and can effectively weaken the dynamic influence of parameters uncertainties and disturbances. Theoretical analysis and simulation results show the effectiveness of the proposed global integral sliding mode control scheme.

Abstract:Rapid lunar exact-landing trajectory optimization was studied by combining a new optimal control method-Gauss Pseudospectral Method (GPM) with the traditional direct shooting method. Landing dynamics equation in high precision model was educed. Aiming at the characters of optimization method and the difficulties in optimization of lunar soft landing trajectory with many constraints, a serial optimization strategy was proposed. Firstly, control variables and state variables were dispersed, and control variables and flying time were used as optimal variables. By giving fewer Gauss nodes, initial values were obtained using GPM, and a serial optimization framework was adopted to obtain the optimal solution from a feasible solution. Then the control variables were dispersed at Gauss nodes, the precise optimal solution was obtained by direct shooting method. Simulation results show that the methodology and strategy for the optimal trajectory design have good robustness and strong convergence.

Abstract:New requirements for design of Supersonic Cruise Missile(SCM) have been brought forward with the technology development of defense systems. The technology of SCM general scheme design centering on a core of effectiveness was discussed preliminarily in this paper, considering the deficiency of traditional performance based design method for the new design requirements of SCM. Development of design technology for missile weapons abroad was firstly analyzed, and it is pointed out that the design technology is oriented toward a direction of effectiveness-centered design; the concept of effectiveness based design is brought forward, which is a certain kind of optimal design of pursuing a satisfying design; technology frame with penetration effectiveness based design was constructed under such new design concept. Main aspects were concentrated on the penetration effectiveness based SCM design frame, foundation of the penetration effectiveness, foundation of the technology, basic modes and several key technologies, etc.

Abstract:An analytical method of coarse alignment in flight based on quaternion which can be used in landing system was presented without any restrictive condition of dynamic process and flight stability. The formula of the coarse alignment which can solve the attitude of the airplane with the velocity measured by GNSS and specific force measured by inertial measurement unit were derived. The factors affecting the alignment performance were analyzed. The simulation results show that the method can be carried out in wide dynamic range with high accuracy, high speed and low computer complexity and can satisfy the requirement of speed and .precision of flight coarse alignment.

Abstract:A new equilibrium-glide state-feedback guidance method based on generalized reference-trajectory was presented for the glide of long-range boost-glide vehicles, considering all path constraints. The 3DOF dynamic equations of boost-glide vehicles were established, and the path constraints were specified. Next, the principle of the guidance method was explained in detail. At the same time, the basis guidance law was designed, and its longitudinal parameter was set by LQR (linear quadratic reentry guidance methods), the new guidance method adjusted the trajectory by the change of angle of attract, and the bank angle profile was small through the glide phase. The simulations show that the new guidance method can satisfy the glide guidance problem of long-range boost-glide vehicles, and have the characteristics of being robust and adaptive. 

Abstract:Flutter analysis plays a vital role in the design of hypersonic airfoil skin. This research introduces the differential quadrature method into the aeroelastic problem of hypersonic skin. The aeroelastic model was presented based on the elasticity theory, and the hypersonic piston theory was used for the modeling of supersonic aerodynamic loads. The validity of the differential quadrature method was confirmed by comparing the FEM solutions for the natural frequencies and the flutter velocity of the airfoil skin, and the relative error is 0.58%. A detailed parametric study was carried out to study the influences of the thickness, area and aspect ratio on the hypersonic flutter behavior of airfoil skins. The result shows that, the flutter velocity increases with the aspect ratio and thickness increased, and decreases with the area increased. 

Abstract:The variable emissivity coatings or devices, based on thermochromism and electrochromism, have great application prospects to spacecraft thermal control, because of their lightness, low energy consumption and facility. The variable emissivity materials are the key of these coatings and devices, and mainly have two kinds: electrochromic materials and thermochromic materials. The application principles of variable emissivity materials on spacecraft thermal control were analyzed. The research progress of four kinds of representative variable emissivity materials, which are perovskite oxides (A_1-xB_xMO₃), vanadium dioxide (VO₂), tungsten trioxides(WO₃) and conducting polymers (CPs) respectively, are preferentially presented. Based on the total needs of spacecraft thermal control, the development trend of variable emissivity materials is discussed finally．

Abstract:The electrochemical properties of lithium sulfur batteries at different temperature were investigated by charge-discharge and CV(Cyclic Voltammetry) for probing into the effect of the liquid diffusion process on discharge process of the lithium-sulfur batteries. Surface morphology of sulfur cathodes was observed by SEM(scanning electron microscope). The surface of sulfur cathode was covered by a solid film in low temperature. It suggests that low temperature results in the decrease of diffusion coefficient and diffusion flux of electrolyte for the battery. The discharge properties of lithium sulfur batteries worsens obviously at less than 10 ℃ and below, and the decrease of low plateau specific capacity was mostly the cause of the worsening. The cyclic voltammetry showed that low plateau of discharge process was strongly affected by temperature because it was a diffusion-controlled process which can lead to polarization in cathode. The increase of diffusion resistance of ion in electrolyte caused the passivation of the carbon matrix, the passivation resulted in inadequate reaction of active material in low plateau, that is mostly the cause of the effect of temperature on discharge process of lithium sulfur batteries.

Abstract:In order to study the effect of mismatched spacing and angle of zero-dispersion femtosecond pulse shaping system on the temporal properties of the output femtosecond pulses, the relation between the resolution and the mismatched spacing of the system was analyzed in theory. And then the effect of mismatched spacing and angle on the system efficiency and the width of the output pulses were discussed. The experimental results indicated that lens misalignment can broaden the pulse, and the influences of the first and the second gratings are symmetrical. Moreover, the influence on system efficiency of angle misalignment was more serious than spacing misalignment. If 600 lines per millimeter grating and lens of 30 centimeter focal length were used, when the angle misalignment was smaller than 9°and spacing misalignment was shorter than 0.5 centimeters, the changing of system efficiency and pulse width were both smaller than 5%. All the results above are helpful to an in-depth study on the zero-dispersion pulse shaping system.