Three decades ago,a highly nonlinear nonpertubative phenomenon,now well-known as the high harmonic generation(HHG),was discovered when intense laser irradiates gaseous atoms.As the HHG produces broadband coherent radiation,it becomes the most promising source to obtain attosecond pulses.The door to the attosecond science was opened ever since.In this review,we will revisit the incredible adventure to the attoworld.Firstly,the progress of attosecond pulse generation is outlined.Then,we introduce the efforts on imaging the structures or filming the ultrafast dynamics of nuclei and electrons with unprecedented attosecond temporal and Angstrom spatial resolutions,utilizing the obtained attosecond pulses as well as the high harmonic spectrum itself.
Many evidences have showed that some intelligence agencies(often called big brother)attempt to monitor citizens’communication by providing coerced citizens a lot of subverted cryptographic algorithms and coercing them to adopt these algorithms.Since legalized services on large number of various applications and system architectures depend on digital signature techniques,in the context some coerced users who use double authentication preventing signatures to design some novel digital signature techniques,have some convincing dissertations to defuse requests from authorities and big brothers creating some corresponding subverted signatures.As rapid progress in quantum computers,National Security Agency advisory memorandum and announcement of National Institute of Standards and Technology procedures from standardization focus on some cryptographic algorithms which are post quantum secure.Motivated by these issues,we design an algorithm substitution attack against Fiat-Shamir family based on lattices(e.g.,BLISS,BG,Ring-TESLA,PASSSign and GLP)that are proven post-quantum computational secure.We also show an efficient deterable way to eliminate big brother’s threat by leaking signing keys from signatures on two messages to be public.Security proof shows that our schemes satisfy key extraction,undetectability and deterability.Through parameters analysis and performance evaluation,we demonstrate that our deterring subverted Fiat-Shamir signature is practical,which means that it can be applied to privacy and protection in some system architectures.
LIU JinhuiYU YongWU FushengCHENG YuehuaZHANG Huanguo
The estimation of sequence or symmetrical components and frequency in three-phase unbalanced power system is of great importance for protection and relay.This paper proposes a new H∞filter based on sparse model to track the sequence components and the frequency of three-phase unbalanced power systems.The inclusion of sparsity improves the error convergence behavior of estimation model and hence short-duration non-stationary PQ events can easily be tracked in the time domain.The proposed model is developed using l1 norm penalty in the cost function of H∞filter,which is quite suitable for estimation across all the three phases of an unbalanced system.This model uses real state space modeling across three phases to estimate amplitude and phase parameters of sequence components.However,frequency estimation uses complex state space modeling and Clarke transformation generates a complex measurement signal from the unbalanced three-phase voltages.The state vector used for frequency estimation consists of two state variables.The proposed sparse model is tested using distorted three-phase signals from IEEE-1159-PQE database and the data generated from experimental laboratory setup.The analysis of absolute and mean square error is presented to validate the performance of the proposed model.
