428 results about "Symbolic execution" patented technology

A method and apparatus for transmitting uplink acknowledge information (ACK) in a communication system using an orthogonal frequency division multiple access (OFDMA) scheme. The method includes receiving a data bit for the uplink ACK; outputting codewords corresponding to the data bit; performing quadrature phase shift keying (QPSK) modulation on symbols for ACK vector indexes corresponding to the codewords for the received data bit; performing inverse fast Fourier transform (IFFT) on a transmission signal having subcarrier clusters to which the modulated transmission symbols are allocated; and transmitting the IFFT-processed transmission signal.

The invention provides a detector for binary-code buffer-zone overflow bugs, and a detection method thereof. The detector comprises six functional modules, namely a debugger module, an input point positioning module, a disassembling module, a symbolic execution module, a loop operation analysis module and an intelligent FUZZ test module. Differing from static symbolic execution, the detection method dynamically loads programs through the self-developed debugger module to synchronously performing symbolic execution and single-step practical execution, and then applies a model to solve each difficulty in binary code analysis so as to test path coverage and detect overflow bugs in accordance with all executable programs of PE format under a Windows platform. The detection can also provide propagation paths of input data and other important information related to bug formation cause while positioning the bugs, only analyzes the selves of the executable programs, needs no source codes, is unrelated to the species of source codes and development tools, and is extensive in applicable occasions, so the detection method has good prospects for popularization and application.

In accordance with a particular embodiment of the present invention, a method is offered that includes generating a symbolic string manipulation class library for one or more web applications. The manipulations are generalized into a string manipulation symbolic algebra. The method also includes performing symbolic execution for one or more web applications. Typically, a Java model checker is augmented to check for certain types of requirements or properties in performing the symbolic execution. If an error scenario exists, a solution to a set of symbolic constraints is obtained, and the solution is mapped back to a source code to obtain an error trace and a test case. In still other specific embodiments, requirements or properties are encoded through templates and checked using public domain decision procedures. The properties or requirements can relate to security validation. The symbolic execution can be customized and tuned for Java-based web applications.

Provided are an excavating device and an excavating method of binary system program loopholes. The excavating device is provided with a static analysis module, a debugger module, a genetic algorithm module, a test input generation module and an abnormal monitoring module which are sequentially connected and a dynamic pollution tracking module located between the debugger module and the genetic algorithm module. The excavating device is guided to generate a test case by aid of a fitness function of the genetic algorithm, the multi-objective fitness function is designed, and the test case is evaluated in view of quantification. Dynamic pollution tracking is used for identifying key bytes in input files to narrow search space of the genetic algorithm. The excavating device combines advantages of the genetic algorithm and the dynamic pollution tracking and is guided to generate the test case, so that the generated test case is strong in pertinence, generated test data are high in accuracy and efficiency, further qualitative analysis and quantitative calculation are combined, and therefore path explosion in binary system program testing based on the symbolic execution and constraint solving technology is avoided.

Demodulator architectures for processing a received signal in a wireless communications system. The demodulator includes a number of correlators coupled to a combiner. Each correlator typically receives and despreads input samples (which are generated from the received signal) with a respective despreading sequence to provide despread samples. Each correlator then decovers the despread samples to provide decovered "half-symbols" and further demodulates the decovered half-symbols with pilot estimates to generate correlated symbols. The decovering is performed with a Walsh symbol having a length (T) that is half the length (2T) of a Walsh symbol used to cover the data symbols in the transmitted signal. The combiner selectively combines correlated symbols from the assigned correlators to provide demodulated symbols. One or more correlators can be assigned to process one or more instances of each transmitted signal. The pilot estimates used within each assigned correlator to demodulate the decovered half-symbols are generated based on the signal instance being processed by that correlator.

A method of sending data in a multiple antenna system according to an aspect of the present invention includes performing precoding on received symbols based on a second codebook generated from a first codebook for a plurality of transmission antennas and sending the precoded symbols. The second codebook is a codebook for transmission antennas which are a multiple of an integer of the plurality of transmission antennas, and a precoding matrix included in the second codebook is generated by a combination of precoding matrices included in the first codebook.

A method and apparatus are provided for analyzing software programs. The invention combines data flow analysis and symbolic execution with a new constraint solver to create a more efficient and accurate static software analysis tool. The disclosed constraint solver combines rewrite rules with arithmetic constraint solving to provide a constraint solver that is efficient, flexible and capable of satisfactorily expressing semantics and handling arithmetic constraints. The disclosed constraint solver comprises a number of data structures to remember existing range, equivalence and inequality constraints and incrementally add new constraints. The constraint solver returns an inconsistent indication only if the range constraints, equivalence constraints, and inequality constraints are mutually inconsistent.

A method for data transmission is disclosed. The method includes: performing, by a system, resource element mapping on modulation symbols which include data to be transmitted and reference signals and which are allocated to antenna ports of a designated type; performing antenna port mapping on the modulation symbols which are through the resource element mapping; and generating Orthogonal Frequency Division Multiplexing (OFDM) signals based on the modulation symbols which are through the antenna port mapping and transmitting the OFDM signals via physical antennas. The present invention also discloses an apparatus for data transmission. In the method and apparatus provided by the present invention, through establishing a mapping relationship between physical antenna elements and antenna ports, beamforming weights are added to modulation symbols of users at the same time. Thus, beamforming operation of the users is implemented. Accordingly, the system may support flexible beamforming transmission on frequency-domain, which greatly improves the flexibility of data transmission of the system.

The invention discloses an Android application strengthening method based on dynamic execution of dex and so files. Through an encryption method, key codes of an Android application are strengthened such that codes of the Android application are protected. The strengthening method comprises an encryption process and a decryption process and comprises following steps: strengthening key codes of the Android application during the encryption process; and decrypting when dynamic execution of the Android application. The Android application strengthening method based on dynamic execution of dex and so files has following beneficial effects: the C++ language is utilized for writing core dex decryption functions so that difficulty in decompilation is increased and the dex decryption functions are present in the form of a dynamic link library and encrypted; compared with the method of core dex dual encryption, key codes of the dynamic link library are encrypted and a JNI calling mechanism is removed during encryption; therefore, plaintext so files encrypted during encryption do not exist in a hard disk and stored in a memory; and the Android application strengthening method is higher in safety.

The invention discloses a static taint analysis and symbolic execution-based Android application vulnerability discovery method, and mainly aims at solving the problems that the analysis range is fixed, the memory consumption is huge and the analysis result is mistakenly reported in the process of discovering vulnerabilities by using the existing static taint analysis method. The method is realized through the following steps of: 1) configuring an analysis target and decompiling a program source code; 2) carrying out control flow analysis on the decompilation result; 3) selecting a source function by a user according to the control flow analysis result, so as to narrow an analysis target; 4) carrying out data flow analysis according to the control flow analysis result, so as to generate a vulnerability path; and 5) filtering the data flow analysis result by adoption of a static symbolic execution technology, taking the residual parts after the filtration as discovered vulnerabilities, warning the user and printing the vulnerability path. On the basis of the existing static taint analysis technology, the method disclosed by the invention has the advantages of extending the vulnerability discovery range, decreasing the memory consumption of vulnerability discovery and improving the accuracy of vulnerability discovery results, and can be applied to the discovery and research of Android application program vulnerabilities.

An OFDM communication system performs time domain channel estimation responsive to received symbols before the symbols are processed by a fast Fourier transform. The communication system generates virtual pilots from actual pilots to improve the stability and quality of channel estimation. The system generates a reference signal from the actual and virtual pilots and correlates the resulting reference signal with a signal responsive to the received symbol to generate an initial channel impulse response (CIR) and to determine statistics about the channel. In some circumstances, the resulting reference signal is correlated with a modified symbol in which the actual and virtual pilot locations are emphasized and the data locations are deemphasized. Time domain channel estimation iteratively improves on the initial CIR. The system determines channel estimates for data only symbols through averaging such as interpolation.

The invention relates to a mode-based dynamic vulnerability discovery integrated system and a mode-based dynamic vulnerability discovery integrated method. The mode-based dynamic vulnerability discovery integrated system comprises a dynamic taint analysis module, a test case selection module, a restraint solving module and a management module. The mode-based dynamic vulnerability discovery integrated method comprises the following steps: firstly, transmitting a seed case to an application program, tracking the transmission of taint data in the program by use of the dynamic taint analysis module, then expressing a transmission track by use of symbols, thereby obtaining a symbolized taint transmission path by virtue of combination of a dynamic taint analysis technology and a symbol execution technology; then by taking the symbolized taint transmission path as input of the restraint solving module, performing restraint solving to obtain a new test case, re-transmitting the test case to the application program, and further performing subsequent operations, wherein the whole process is performed under unified dispatching management of the management module. According to the mode-based dynamic vulnerability discovery integrated system and the mode-based dynamic vulnerability discovery integrated method, the automation degree and efficiency of dynamic vulnerability discovery for a binary program are improved, the generated test data accuracy and the efficiency are high, and thus a fuzzy test process is high in pertinency.

A digital communication system based on the use of chaotic carriers is disclosed. For each symbol to be sent, the transmitter sends a reference chaotic signal followed by a transformed version of the reference chaotic signal. For different symbols, different transformations are performed. Also, the transformations are designed such that the transformed versions of the reference chaotic signal do not resemble the original reference chaotic signal. As a consequence, little information can be deduced by inspecting the frequency spectrum of the transmitted signal. Moreover, even if the communication could be detected, it is difficult to decode the messages because there are numerous transformations possible.

Embodiments of the present invention include a method for performing joint time synchronization and carrier frequency offset estimation in a wireless communication system, comprising steps of: on a transmitter: performing frequency domain spreading and interleaving on input data by using a predetermined spreading factor (SF) to generate a frequency domain training symbol; performing Inverse Discrete Fourier Transformation (IDFT) on the generated frequency domain training symbol to generate a first time domain training symbol; reversely copying the generated first time domain training symbol to a second time domain training symbol such that a complete training sequence is formed; and on a receiver: detecting an average power of received signals to judge the coming of a training sequence, and performing coarse frame synchronization; performing joint fine frame synchronization and carrier frequency offset estimation based on a received training sequence; and compensating for the carrier frequency offset based on the carrier frequency offset estimation result so as to eliminate the carrier frequency offset. In addition, embodiments of the present invention also include an apparatus for performing joint time synchronization and carrier frequency offset estimation and a method for generating a training sequence.

A “property checker” uses light-weight symbolic execution to prove that software programs satisfy safety properties by simultaneously performing program testing and program abstraction. A simple example of safety properties includes conditions that must be satisfied for proper program execution, such as whether an application properly interfaces with API methods or functions. Program tests are an “under-approximation” of program behavior, and abstractions are an “over-approximation” of the program. This simultaneous testing either finds a test-case that reaches an error state, or finds an abstraction showing that no path in the state space of the program can reach any error state. If a test-case reaches an error state, the property checker has discovered a violation of the safety property. Conversely, if no path in the state space can reach any error state, the property checker has proved that the program satisfies the desired safety property.

A method for performing speed dialing using symbols in a communication terminal having a touch pad is disclosed. The method comprises registering a symbol in association with a phone number; comparing a symbol input by a user from the touch pad with the registered symbol; and reading, when the input symbol is identical to the registered symbol, said phone number registered in associated with the registered symbol and automatically dialing the read phone number. An error message, or a re-input request message, is displayed when the input symbol is not identical to a registered symbol.

A method for channel response estimation for an OFDM communication system based on a certain normal training symbols plus one virtual training symbol begins with receiving at least one preamble symbol of a transmitted data frame. A first channel state information is estimated from the at least one preamble symbol. At least one signalling symbol is then received and equalized and a rate factor and a length factor are extracted from the at least one signalling symbol. A virtual training symbol is formed from the rate factor and the length factor. A second channel state information is estimated from the at least one preamble symbol and the virtual training symbol. The data symbols are equalized by performing channel correction on data symbols with the second channel estimation and pilot sub-carriers in each of the plurality of data symbols.

The invention discloses a vulnerability detection system aiming at binary executable files and combining fuzz testing with symbolic execution, belongs to computer vulnerability detection software development technology and aims to increase detection depth and improve detection efficiency in binary file vulnerability detection scenes. The vulnerability detection system comprises a fuzzifier modulethrough optimization design, a symbolic execution module through optimization design and a fuzzifier skip symbol scheduling execution module, and a cache explorer and a task cooperation module are introduced. Advantages of fuzz testing and symbolic execution are combined for vulnerability detection of binary execution files. Evaluation experiments are conducted on the system, an application program provided by a qualification test of DARPA network challenge is adopted as a dataset, and contrast experiments are set on three objects including single fuzz testing, single symbolic execution and avulnerability mining system realized by the system. The system has remarkable effect, exploration of binary program compartment is accelerated, and running speed of the vulnerability mining system isincreased greatly.

Disclosed is a receiver of a direct conversion receiving scheme in which a packet is transmitted or received while performing frequency hopping for each symbol and demodulation is started by carrier sensing at the beginning of the packet, which performs demodulation without hopping frequencies of LOs of receiving systems to reliably execute fast carrier sensing and hopping synchronization at the beginning of the packet and remove the DC offset jump. At a time of demodulation of a payload part, the frequencies of LOs of the receiving system are hopped to allow a transition of MIMO. Further, by concurrently using complex bandpass filters while fixing all the LOs at a center LO frequency, complete removal of the DC offset jump over the entire length of the packet and MIMO can be simultaneously implemented.