CN116594040A - Civil anti-fake navigation signal generation and receiving method based on spread spectrum code random processing - Google Patents

Abstract

The application provides a civil anti-counterfeiting navigation signal generation and receiving method based on spread spectrum code random processing, which comprises the following steps: randomly generating an authentication root key pair of a pair of public key cryptosystems as an authentication base key pair; signing a digital signature on a navigation message in a certain period, obtaining a basic authentication spread spectrum code from the navigation message in the next period through a secure computing technology, and modulating the digital signature onto the basic authentication spread spectrum code to obtain an authentication mark sequence; obtaining a flipped mixed spread spectrum code; and combining the overturned spread spectrum code with the navigation message and the carrier wave to generate a navigation signal. The signal receiving method comprises two receiving processing modes of a slow channel and a fast channel, wherein the two receiving processing modes can respectively and independently obtain the result of navigation signal authentication. By using the method provided by the application, the navigation signal authentication with high reliability and high safety can be realized under the conditions of moderate calculated amount and no need of the buffer signal sampling of the user terminal.

Description

Civil anti-fake navigation signal generation and receiving method based on spread spectrum code random processing

Technical Field

The application relates to the technical field of satellite navigation, in particular to an anti-counterfeiting and anti-deception signal system applied to civil satellite navigation, and more particularly relates to a civil anti-counterfeiting navigation signal method, system and medium based on spread spectrum code random processing.

Background

With the development of modern satellite navigation systems such as Beidou systems, GPS, galileo and GLONASS, more and more civil key infrastructures and life safety services represented by finance, electric power, unmanned aerial vehicles and automatic driving begin to provide accurate time and position information depending on satellite navigation. On the other hand, a large number of experiments and cases also show that the civil navigation signal without authentication is easily attacked by the deception signal, so that the time and the position obtained by the navigation receiver through resolving are controlled by the deception attacker, and the security of satellite navigation service is further threatened. Obviously, in order to protect the reliability and security of civil critical infrastructure and life safety services when using satellite navigation services, it is necessary to authenticate the authenticity of the satellite navigation signals.

The core idea of the satellite navigation signal authenticity authentication is as follows: a piece of information that is easy to verify but difficult to forge is generated and attached to the satellite navigation signal, and the receiver confirms the authenticity of the satellite navigation signal by extracting and verifying this authentication information. The satellite navigation signal is a direct sequence spread spectrum signal and consists of a navigation message, a spread spectrum code and a radio frequency carrier, and most of the navigation signal authentication technologies reported in literature are mainly realized by authenticating the navigation message information and the spread spectrum code sequence. The navigation message information authentication has the characteristics of high detection probability and low implementation complexity of a receiver, but because the symbol rate of most satellite navigation messages is about 100bps, the time resolution or the characteristic symbol width of the authentication is the navigation message bit width (namely about 10 ms), so that short-delay forwarding type or regenerative deceptive signals with the delay difference from real signals smaller than the navigation message bit width are difficult to effectively detect, and a certain security hole exists. On the other hand, spreading code authentication benefits from the higher rate of spreading codes, and has the characteristic of high authentication time resolution, but part of currently known spreading code sequence authentication needs the assistance of a third party communication link and cannot realize self-closed loop authentication in a navigation system, and the other part of the currently known spreading code sequence authentication requires a receiver to cache quite long original signal samples (usually a few seconds), so that extremely large data storage overhead is introduced, and great difficulty is encountered in the complexity of the implementation of the receiver, and the wide popularization of the receiver is hindered.

Aiming at the design difficulty of the current satellite navigation signal authenticity authentication signal, an anti-counterfeiting navigation signal system with high authentication time resolution, high detection probability and low receiver realization cost is urgent.

Disclosure of Invention

The application provides a civil anti-counterfeiting navigation signal method, system and medium based on random processing of a spread spectrum code, which are used for realizing navigation signal anti-deception authentication with high authentication time resolution, high detection probability and low cost realized by a receiver, solving the problems that the navigation message authentication time resolution is low and the spread spectrum code authentication needs a large amount of data buffering or communication system assistance, and providing a receiving and authentication method of the signal system.

The first aspect of the application discloses a civil anti-counterfeiting navigation signal generation method based on spread spectrum code random processing, which comprises the following steps:

step S1, randomly generating an authentication root key pair of a pair of public key cryptosystems as an authentication base key pair;

s2, signing a digital signature on the navigation message in the period according to the authentication basic key pair in the step S1, obtaining a basic authentication spread spectrum code from the navigation message in the next period, and modulating the digital signature on the basic authentication spread spectrum code to obtain an authentication mark sequence;

step S3, generating a random key as an authentication key for the current period, and generating a mark whether each signal chip in the public periodic spread spectrum code in the current period corresponds to processing or not, namely the positions of all processed spread spectrum chips in the public periodic spread spectrum code by taking the authentication key as a key and the signal time in the current period as a seed;

the specific determination method of the processing position comprises the following steps:

in the spread spectrum code of the anti-fake navigation signal, the spread spectrum code is marked as the interval of fixed number of chipsPerforming segmentation, inside each segment, before->Chip or post->The periodic public spreading code of the chip is marked as +.>The spreading code chip of (2) is in a processing state, and the flip spreading code is indicated by the processing indication sequence +.>Determining that the treatment indicates the sequence->Is a sequence consisting of 0 and 1, the spreading code corresponding to the time point with the value of 1 is processed, and the sequence is marked by authentication +.>Determining that each spreading code is front +.>The chip is also post +.>The code chip, the authentication mark sequence is a sequence with a value of + -1, and the time with a value of +1 corresponds to the back +.>The chip contains the processed spread code, and the time with the value of-1 corresponds to the former +.>The code chip contains processed spread spectrum code, the spread spectrum code of the anti-fake navigation signal +.>Can be expressed in the following form:

，

wherein Is the original public periodic spreading code, < >>Is the spreading code rate,/->Is a navigation authentication mark sequence,/->Is a processing instruction sequence, t represents the corresponding time in the period; treatment instruction sequence->Calculated by the following formula:

，

wherein Is a sequence with a value of 0 or 1, < >>The method is a transformation method taking k as a secret key and a plaintext, and t is signal time; the transformation method comprises the following steps:

s31, the signal time is accurate to a spread spectrum code chip, the starting moment of the spread spectrum code chip is taken, 8 time parameters of the code chip number in year, month, day, time, minute, second, millisecond and millisecond are respectively converted into binary sequences with the lengths not less than 16bit, 5bit, 6bit, 7bit, 10bit and 16bit, and the binary sequences with the lengths not more than 96bit are combined;

step S32, according to the spread spectrum code period belonging to public authentication or user pointing authentication, taking a 32bit binary string as a characteristic word; if the current period belongs to public authentication, the binary string takes all 0 feature words, otherwise, takes 32bit feature words corresponding to the user ID;

step S33, connecting the 96bit time sequence with the 32bit feature word to obtain 128bit turning position generation information as a block plaintext, then taking the current authenticated key as a key, and calculating by using a block cipher algorithm to obtain 128bit ciphertext;

step S34, regarding the whole 128-bit ciphertext as a decimal number, if the decimal number is larger than the decimal numberThenOtherwise->； wherein />The proportion of the processing chips in the whole spread spectrum codes is calculated;

step S35, repeating steps S31 to S34, and generating an indication of whether each spreading code should be processed or not in the required time range;

the processing specifically adopts spread spectrum BPSK, BOC or MSK modulation modes based on spread spectrum code modulation to set different processing modes according to the anti-counterfeiting navigation signal:

for BPSK modulation, the polarity of the spread spectrum code chip is directly inverted, namely +1 chip is modified into-1 chip, and-1 chip is modified into +1 chip; for BOC modulation, the phase sequence of the sub-carriers is adjusted by half cycle, namely, the sub-carriers in 01 sequence are adjusted to be 10, and the sub-carriers in 10 sequence are adjusted to be 01; for MSK modulation mode, the frequency offset is circularly shifted and adjusted, namely the original frequency shiftAdjust to->, wherein />Is the turnover adjustment quantity-> and />The lowest and highest frequencies allowed by the signal band, respectively;

step S4, according to the authentication mark sequence obtained in the step S2, setting a section of spreading code corresponding to each element of the authentication mark sequence in a period of a public periodic spreading code, and in the first half or the second half of the public periodic spreading code of the navigation signal, wherein the first half or the second half is determined by the mark of the corresponding element of the authentication mark sequence, processing signal chips of the public periodic spreading code based on the processing position obtained in the step S3, and obtaining a processed mixed spreading code;

and S5, combining the processed mixed spread spectrum code obtained in the step S4 with the navigation message and the carrier wave to generate a navigation signal.

According to the civil anti-counterfeiting navigation signal generation method based on the random processing of the spread spectrum code, in the step S1, a public key cryptosystem SM2 or ECDSA is used.

According to the civil anti-counterfeiting navigation signal generation method based on the random processing of the spread spectrum code, in the step S2, a digital signature is modulated onto a basic authentication spread spectrum code in a CSK modulation mode, and an authentication mark sequence is obtained.

According to the civil anti-counterfeiting navigation signal generation method based on the random processing of the spread spectrum code, a BPSK modulation mode is adopted, and the mathematical expression of the anti-counterfeiting navigation signal is as follows:

wherein ,is signal power, +.>Is a navigation message, & lt + & gt>An authenticated and modified spreading code +.>Is the carrier frequency, < >>The initial carrier phase j is an imaginary unit, t is signal time, and the anti-fake information is carried on the spread spectrum code of the navigation signal and broadcast to the user along with the navigation signal.

The application discloses a civil anti-counterfeiting navigation signal receiving method based on spread spectrum code random processing, which is used for receiving signals generated by the civil anti-counterfeiting navigation signal generating method based on the spread spectrum code random processing in one of the first aspect, wherein the receiving method comprises two receiving processing modes of a slow channel and a fast channel.

According to the civil anti-counterfeiting navigation signal receiving method based on the random processing of the spread spectrum code disclosed by the second aspect of the application, the method comprises the following steps in a slow channel processing mode:

step S61, the receiver captures and tracks the navigation signal, and the correlation value and the navigation message of the on-time branch are proposed from the tracking channel;

step S62, before the complete navigation message of an authentication period is received, the receiver firstly caches the adjacent difference result of the on-time branch related value as the observed quantity of the authentication mark sequence; after the navigation message of one authentication period is completely received, the receiver calculates the authentication mark spread spectrum code of the current authentication period from the navigation message through the derivation algorithm of the authentication mark spread spectrum code;

step S63, the receiver uses the authentication mark spread spectrum code of the authentication period and the cached authentication mark sequence observed quantity to carry out correlation calculation, and the digital signature carried in the digital signature is obtained through a CSK demodulation algorithm;

in step S64, the receiver uses the public key of the public asymmetric cryptosystem to verify the consistency of the navigation message and the digital signature, and obtains the result of the navigation signal authentication.

According to the civil anti-counterfeiting navigation signal receiving method based on the random processing of the spread spectrum code disclosed by the second aspect of the application, under a fast channel processing mode, the steps are as follows:

step S71, the receiver acquires the authentication key and generates a spread spectrum code processing position according to the signal time, or receives the spread spectrum code processing position of the time period near the current moment;

step S72, according to the indication of the spreading code processing position, the receiver extracts the corresponding signal sampling observation, and carries out correlation operation with the signal sampling observation by using the processed spreading code;

in step S73, the receiver performs the hypothesis testing procedure of the authentication detector with the correlation operation result as the authentication detection amount, and obtains the result of the signal trusted authentication.

In summary, the scheme provided by the application has the following technical effects: the civil anti-counterfeiting navigation signal generation and receiving method based on the spread spectrum code random processing provided by the application can realize high-reliability and high-safety navigation signal authentication under the conditions of moderate calculated amount and no need of user terminal buffer signal sampling. And the navigation signal authentication spread spectrum code occupies smaller space, and has smaller influence on the terminal without authentication.

Drawings

In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the drawings that are needed in the description of the embodiments or the prior art will be briefly described, and it is obvious that the drawings in the description below are some embodiments of the present application, and other drawings can be obtained according to the drawings without inventive effort for a person skilled in the art.

Fig. 1 is a schematic diagram of a spreading code flip structure of a BPSK-based civil anti-counterfeiting navigation signal system provided by the present application;

FIG. 2 is a layered time domain structure diagram of a civil anti-counterfeiting navigation signal system provided by the technology of the application;

FIG. 3 is a schematic diagram of the relationship between the digital signature of the civil anti-counterfeiting navigation signal system and the password student of the navigation message provided by the technology of the application;

FIG. 4 is a schematic diagram of an exemplary authentication processing architecture of a GNSS receiver of a civil anti-counterfeiting navigation signal system according to the present application;

fig. 5 is a schematic flow diagram of a signal generation method of a civil anti-counterfeiting navigation signal system provided by the technology of the application;

FIG. 6 is a schematic diagram of a specific generation structure and parameter setting hierarchy of an anti-counterfeiting navigation signal in an embodiment of a civil anti-counterfeiting navigation signal system provided by the present application;

FIG. 7 is a flowchart of another specific generation method of an anti-counterfeiting navigation signal according to an embodiment of the present application;

fig. 8 is a schematic diagram of a manner of turning over a spreading code of an anti-counterfeiting information guide signal provided by the technology of the present application.

Detailed Description

For the purpose of making the objects, technical solutions and advantages of the embodiments of the present application more apparent, the technical solutions of the embodiments of the present application will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present application, and it is apparent that the described embodiments are only some embodiments of the present application, not all embodiments of the present application. All other embodiments, which can be made by those skilled in the art based on the embodiments of the application without making any inventive effort, are intended to be within the scope of the application.

Fig. 1 is a schematic diagram of a spreading code flip structure of a BPSK-based civil anti-counterfeiting navigation signal system, which includes an authentication flag sequence, a signal spreading code, and a flip indication sequence. For BPSK modulation, the polarity of the spread spectrum code chip is directly inverted, namely +1 chip is modified into-1 chip, and-1 chip is modified into +1 chip; for BOC modulating, namely carrying out half cycle adjustment on the phase sequence of the subcarriers, namely adjusting the subcarrier in the 01 sequence to be 10, and adjusting the subcarrier in the 10 sequence to be 01; for MSK modulation mode, the frequency offset is circularly shifted and adjusted, namely the original frequency shiftIs adjusted to, wherein />Is the turnover adjustment quantity-> and />The lowest and highest frequencies allowed by the signal band, respectively.

Fig. 5 is a schematic flow chart of a method for generating civil anti-counterfeiting navigation signals based on random inversion of spreading codes, which is provided by the first technology of the present application, and is illustrated by taking BPSK signals as an example, the method comprises four steps:

step S1, randomly generating an authentication root key pair of a pair of public key cryptosystems as an authentication base key pair.

In said step S1, a public key cryptosystem SM2 or ECDSA is used; the security calculation in step S2 is a hash algorithm or a block cipher algorithm.

And S2, signing a digital signature on the navigation message in the period according to the authentication basic key pair in the step S1, obtaining a basic authentication spread spectrum code from the navigation message in the next period through a secure computing technology, and modulating the digital signature on the basic authentication spread spectrum code to obtain an authentication mark sequence.

In the step S2, the digital signature is modulated onto the basic authentication spreading code in a CSK modulation mode, and an authentication flag sequence is obtained.

Step S3, generating a random key for the current period as an authentication key, and generating a sign whether each signal chip in the public periodic spread spectrum code in the current period is overturned or not, namely the positions of all overturned spread spectrum chips in the public periodic spread spectrum code by using the authentication key as a key and using a signal sequence number in the current period as a seed through a shuffling algorithm.

In the step S3, the specific method for determining the flip position is to record the spreading code of the anti-fake navigation signal as the interval of a fixed number of chipsPerforming segmentation, inside each segment, before->Chip or post->The periodic public spreading code of the chip is marked as +.>The spread spectrum code chip of (2) is in a reverse state, and the reverse spread spectrum code is represented by a reverse indication sequence +.>Determining, the flip indicator sequence->Is a sequence consisting of 0 and 1, the spreading code corresponding to the time point with the value of 1 is overturned, and the authentication mark sequence +.>Determining that each spreading code is front +.>The chip is also post +.>The code chip, the authentication mark sequence is a sequence with a value of + -1, and the time with a value of +1 corresponds to the back +.>The chip contains the processed spread code, and the time with the value of-1 corresponds to the former +.>The code chip contains processed spread spectrum code, and the spread spectrum code of the anti-fake navigation signalCan be expressed in the following form: />，

wherein Is the original public periodic spreading code, < >>Is the spreading code rate,/->Is a navigation authentication mark sequence,/->Is a processing instruction sequence, t represents the corresponding time in the period; treatment instruction sequence->Calculated by the following formula:

，

wherein Is a sequence with a value of 0 or 1, < >>The method is a transformation method taking k as a secret key and a plaintext, and t is signal time; the transformation method comprises the following steps:

s31, the signal time is accurate to a spread spectrum code chip, the starting moment of the spread spectrum code chip is taken, 8 time parameters of the code chip number in year, month, day, time, minute, second, millisecond and millisecond are respectively converted into binary sequences with the lengths not less than 16bit, 5bit, 6bit, 7bit, 10bit and 16bit, and the binary sequences with the lengths not more than 96bit are combined;

step S32, according to the spread spectrum code period belonging to public authentication or user pointing authentication, taking a 32bit binary string as a characteristic word; if the current period belongs to public authentication, the binary string takes all 0 feature words, otherwise, takes 32bit feature words corresponding to the user ID;

step S33, connecting the 96bit time sequence with the 32bit feature word to obtain 128bit turning position generation information as a block plaintext, then taking the current authenticated key as a key, and calculating by using a block cipher algorithm to obtain 128bit ciphertext;

step S34, regarding the whole 128-bit ciphertext as a decimal number, if the decimal number is larger than the decimal numberThenOtherwise->； wherein />The proportion of the processing chips in the whole spread spectrum codes is calculated;

step S35, repeating steps S31 to S34, may generate an indication of whether each spreading code should be processed within the required time frame.

The anti-counterfeiting navigation signal adopts a spread spectrum BPSK, BOC or MSK modulation mode based on spread spectrum code modulation.

The BPSK modulation mode is adopted, and the mathematical expression of the anti-counterfeiting navigation signal is as follows:

wherein ,is signal power, +.>Is a navigation message, & lt + & gt>An authenticated and modified spreading code +.>Is the carrier frequency, < >>The initial carrier phase j is an imaginary unit, t is signal time, and the anti-fake information is carried on the spread spectrum code of the navigation signal and broadcast to the user along with the navigation signal.

Step S4, according to the authentication mark sequence obtained in the step S2, in a public periodic spread spectrum code period, according to the mode that each element of the authentication mark sequence corresponds to a section of spread spectrum code, in the first half or the second half of the original public periodic spread spectrum code of the navigation signal, wherein the first half or the second half is determined by the polarity of the corresponding element of the authentication mark sequence, and in the turning position obtained in the step S3, the signal code slice of the public periodic spread spectrum code is turned over to obtain a turned-over mixed spread spectrum code;

and S5, combining the overturned spread spectrum code obtained in the step S4 with a navigation message and a carrier wave to generate a navigation signal.

The signal structure generated based on the above steps is shown in fig. 6, and the signal authentication information structure is shown in fig. 8.

Another embodiment of the present application provides a specific implementation of a method for generating a civil anti-counterfeit navigation signal based on spread spectrum code random processing, as shown in fig. 7: generating a root key by randomly generating an authentication root public key and a key chain; generating a root key for the key chain, and continuously calculating a password hash function to obtain the key chain and an authentication root key thereof; extracting a key at a corresponding position in a key chain according to the current signal time; calculating the starting position of a spreading code authentication cluster and the starting position of each period of authentication spreading code in the starting position according to the secret key; replacing the spreading code authentication cluster into a navigation signal spreading code according to the calculated position; filling the authentication root information into a navigation message; and modulating the navigation signal to broadcast to the user in a normal way by using the replaced spread spectrum code and the navigation message.

The novel signal system applied to civil navigation signal anti-counterfeiting authentication, namely the civil anti-counterfeiting navigation signal system based on clustered spread spectrum code position authentication, is described in detail by taking anti-counterfeiting authentication of the Beidou system civil signal B1C as an embodiment.

The technical scheme of the application provides a novel civil anti-counterfeiting navigation signal based on random inversion of a spread spectrum code, which comprises the following characteristics:

the anti-counterfeiting navigation signal adopts a modulation mode such as spread spectrum BPSK, BOC or MSK based on spread spectrum code modulation, and the BPSK modulation is taken as an example, and the mathematical expression of the anti-counterfeiting navigation signal is as follows:

wherein ,is signal power, +.>Is a navigation message, & lt + & gt>An authenticated and modified spreading code +.>Is the carrier frequency, < >>The initial carrier phase j is an imaginary unit, t is signal time, and the anti-fake information is carried on the spread spectrum code of the navigation signal and broadcast to the user along with the navigation signal.

In the spread spectrum code of the anti-fake navigation signal, the spread spectrum code is marked as the interval of fixed number of chipsPerforming segmentation, inside each segment, before->Chip or post->The periodic public spreading code of the chip is marked as +.>The spreading code chip of (2) is in a processing state, and the flip spreading code is indicated by the processing indication sequence +.>Determining that the treatment indicates the sequence->Is a sequence consisting of 0 and 1, the spreading code corresponding to the time point with the value of 1 is processed, and the sequence is marked by authentication +.>Determining that each spreading code is front +.>The chip is also post +.>The code chip, the authentication mark sequence is a sequence with a value of + -1, and the time with a value of +1 corresponds to the back +.>The chip contains the processed spread code, and the time with the value of-1 corresponds to the former +.>The code chip contains processed spread spectrum code, the spread spectrum code of the anti-fake navigation signal +.>Can be expressed in the following form:

，

wherein Is the original public periodic spreading code, < >>Is the spreading code rate,/->Is a navigation authentication mark sequence,/->Is a flip indication sequence, and t represents the corresponding time in the period. The structure of the spread spectrum code flip at this time is shown in fig. 1.

Flipping indication sequenceThe authentication key is combined with the signal time to generate the signal time through a cryptography algorithm, and the signal time is shown as the following formula:

wherein The method is a cipher transformation algorithm with k as a key and a plaintext, and t is signal time. The authentication mark sequence is a digital signature signal spread by a section of secret spreading code, the digital signature is modulated on the spreading code by adopting a BPSK or CSK modulation mode, and the digital signature is signed for the navigation message where the current signal is located.

Fig. 2 shows an overall structure of the anti-counterfeiting authentication signal, which takes CSK as an example. The authentication of the anti-counterfeiting navigation signal is divided into units of periods, and each authentication period comprises a complete digital signature. Each digital signature is in turn divided into N segments according to the parameter settings, each segment determining the cyclic shift size, or initial code phase, of one authentication mark sequence period. Each spreading code chip in the authentication mark sequence corresponds to two segments in the civil spreading code, and according to the definition of the flipping operator, a +1 chip in the authentication mark sequence represents that the second segment in the two civil spreading code segments contains flipped chips, and a-1 chip in the authentication mark sequence represents that the first segment in the two civil spreading code segments contains flipped chips. The position of the flipped chip is controlled by a flipping flag sequence.

The basic authentication mark spread spectrum code is used for modulating a basic period repeated sequence carrying a digital signature, the user is kept secret in the current authentication period broadcasted by the authentication signal, and the user can calculate the sequence of the basic authentication mark spread spectrum code of the current authentication period through the navigation message of the next authentication period. The derived relation between the navigation message and the basic authentication mark spread spectrum code can be realized through a one-way function, and the output of the function has statistical pseudo-random characteristics, thereby meeting the use requirement of the spread spectrum code. For example, the cryptographic hash algorithm family is a good one-way function with a fixed output length, which is easy to compute forward and get pseudo-random output results, and the reverse computation complexity is extremely high. The digital signature is modulated to the basic authentication mark spread spectrum code in a flexible way, and a BPSK mode, a CSK mode and the like can be selected.

Figure 3 shows a schematic representation of the relationship between the digital signature and the navigation message. The digital signature is used to establish a trust basis for the anti-counterfeit authentication signal. The security and trust of the signal is protected by the verifiable nature of the digital signature, and the receiver can verify that the digital signature matches the data it signed (typically the navigation message) by means of a public key of the public asymmetric cryptosystem. At the same time, the nature of the asymmetric cryptographic system makes it almost impossible for an attacker who does not grasp the private key to forge counterfeit data with a valid digital signature. The digital signature used in the anti-counterfeit authentication signal is generated in the navigation satellite by a private key, and the navigation message is a proper information for signing the digital signature. When the public key of this signature is disclosed in the ICD, the receiver can verify the authenticity of the received digital signature by checking if the digital signature matches the navigation message, thereby rendering the navigation message in the broadcast signal verifiable. In addition, the digital signature is carried by the corresponding spreading code of the signal after being modified by the authentication mark sequence, so that time sequence binding can be established between the navigation message and the spreading code. Based on the verification of the digital signature and the timing binding, the joint authentication of the navigation signal message and the spread spectrum code can be realized. The digital signature is used as a trust basis of authentication, and defines an authentication period of navigation signal authentication: signal time range for single digital signature authentication. In each authentication period, the navigation signal authentication information is independent of each other. Considering the security of the authentication method against the generated spoofing attack, the private key of the digital signature is stored in a secret manner by the satellite or the operational control section of the GNSS, and the corresponding public key and the verification algorithm are issued to all users. Thus, the digital signature of each authentication period can be trusted through a signature verification algorithm and a public key of the signature, and the trusted verification can be performed according to the consistency of the signature and the navigation message in the authentication period. In practice, the length of the navigation message segment is typically set to an integer multiple of the frame length to achieve a concise synchronization of signal authentication and message demodulation.

As shown in fig. 4, a typical processing structure of a GNSS receiver with signal authentication capability is shown. The fast and slow channels of the authentication receiver have different processing modes. The slow-path processing mode verifies the digital signature demodulated from fluctuations in correlation results in the tracking loop. The fast channel processing mode verifies whether the signal is authentic by detecting whether there is a flipped chip at the expected flipped position of the spreading code.

In the slow channel processing mode, the receiver first captures and tracks the navigation signal, and the correlation value and navigation message of the on-time branch are extracted from the tracking channel. Before the complete navigation message of one authentication period is received, the receiver firstly caches the adjacent difference result of the on-time branch related value as the observed quantity of the authentication mark sequence. After the navigation message of one authentication period is completely received, the receiver calculates the authentication mark spread spectrum code of the current authentication period from the navigation message through the derivation algorithm of the authentication mark spread spectrum code. And then, the receiver uses the authentication mark spread spectrum code of the authentication period to perform correlation calculation with the cached authentication mark sequence observed quantity, and obtains the digital signature carried in the digital signature through a CSK demodulation algorithm. And finally, the receiver uses the public key of the public asymmetric cryptographic system to verify the consistency of the navigation message and the digital signature, and a navigation signal authentication result is obtained.

In the fast channel processing mode, the receiver needs to acquire the authentication key through the data communication service and generate a spreading code turning position according to the signal time, or receive the spreading code turning position of the time period near the current time through the data communication service. Based on the indication of these flipped positions, the receiver extracts signal sample observations at corresponding positions from the signal samples that were stripped from motion by the tracking channel, and uses these flipped spreading codes to correlate with the extracted signal sample observations. Finally, the receiver uses the relevant operation result as the authentication detection quantity, and executes the hypothesis testing process of the authentication detector to obtain the result of the signal credible authentication.

In summary, the technical scheme provided by the application has the following technical effects: the civil anti-counterfeiting navigation signal generation and receiving method based on random overturn of the spread spectrum code provided by the application can realize high-reliability and high-safety navigation signal authentication under the conditions of moderate calculated amount and no need of user terminal buffer signal sampling, and the spread spectrum code for the navigation signal authentication has smaller occupied area, smaller influence on the terminal without authentication and has an important guiding function in practical application.

Note that the technical features of the above embodiments may be arbitrarily combined, and all possible combinations of the technical features in the above embodiments are not described for brevity of description, however, as long as there is no contradiction between the combinations of the technical features, they should be regarded as the scope of the description. The foregoing examples illustrate only a few embodiments of the application, which are described in detail and are not to be construed as limiting the scope of the application. It should be noted that it will be apparent to those skilled in the art that several variations and modifications can be made without departing from the spirit of the application, which are all within the scope of the application. Accordingly, the scope of protection of the present application is to be determined by the appended claims.

Claims (7)

1. A civil anti-counterfeiting navigation signal generation method based on spread spectrum code random processing is characterized by comprising the following steps:

step S1, randomly generating an authentication root key pair of a pair of public key cryptosystems as an authentication base key pair;

s2, signing a digital signature on the navigation message in the period according to the authentication basic key pair in the step S1, obtaining a basic authentication spread spectrum code from the navigation message in the next period, and modulating the digital signature on the basic authentication spread spectrum code to obtain an authentication mark sequence;

step S3, generating a random key as an authentication key for the current period, and generating a mark whether each signal chip in the public periodic spread spectrum code in the current period corresponds to processing or not, namely the positions of all processed spread spectrum chips in the public periodic spread spectrum code by taking the authentication key as a key and the signal time in the current period as a seed;

the specific determination method of the processing position comprises the following steps:

in the spread spectrum code of the anti-fake navigation signal, the spread spectrum code is marked as the interval of fixed number of chipsPerforming segmentation, inside each segment, before->Chip or post->The periodic public spreading code of the chip is marked as +.>The spreading code chip of (2) is in a processing state, and the flip spreading code is indicated by the processing indication sequence +.>Determining that the treatment indicates the sequence->Is a sequence consisting of 0 and 1, the spreading code corresponding to the time point with the value of 1 is processed, and the sequence is marked by authentication +.>Determining that each spreading code is front +.>The chip is also post +.>The code chip, the authentication mark sequence is a sequence with a value of + -1, and the time with a value of +1 corresponds to the back +.>The chip contains the processed spread code, and the time with the value of-1 corresponds to the former +.>The code chip contains processed spread spectrum code, the spread spectrum code of the anti-fake navigation signal +.>Can be expressed in the following form:

，

wherein Is the original public periodic spreading code, < >>Is the spreading code rate,/->Is a sequence of navigation authentication flags,is a processing instruction sequence, t represents the corresponding time in the period; treatment instruction sequence->Calculated by the following formula:

，

wherein Is a sequence with a value of 0 or 1, < >>The method is a transformation method taking k as a secret key and a plaintext, and t is signal time; the transformation method comprises the following steps:

s31, the signal time is accurate to a spread spectrum code chip, the starting moment of the spread spectrum code chip is taken, 8 time parameters of the code chip number in year, month, day, time, minute, second, millisecond and millisecond are respectively converted into binary sequences with the lengths not less than 16bit, 5bit, 6bit, 7bit, 10bit and 16bit, and the binary sequences with the lengths not more than 96bit are combined;

step S32, according to the spread spectrum code period belonging to public authentication or user pointing authentication, taking a 32bit binary string as a characteristic word; if the current period belongs to public authentication, the binary string takes all 0 feature words, otherwise, takes 32bit feature words corresponding to the user ID;

step S33, connecting the 96bit time sequence with the 32bit feature word to obtain 128bit turning position generation information as a block plaintext, then taking the current authenticated key as a key, and calculating by using a block cipher algorithm to obtain 128bit ciphertext;

step S34, regarding the whole 128-bit ciphertext as a decimal number, if the decimal number is larger than the decimal numberThen->Otherwise->； wherein />The proportion of the processing chips in the whole spread spectrum codes is calculated;

step S35, repeating the steps S31 to S34, and generating an indication whether each spreading code should be processed or not in the required time range;

the processing specifically adopts spread spectrum BPSK, BOC or MSK modulation modes based on spread spectrum code modulation to set different processing modes according to the anti-counterfeiting navigation signal:

for BPSK modulation, the polarity of the spread spectrum code chip is directly inverted, namely +1 chip is modified into-1 chip, and-1 chip is modified into +1 chip; for BOC modulation, the phase sequence of the sub-carriers is adjusted by half cycle, namely, the sub-carriers in 01 sequence are adjusted to be 10, and the sub-carriers in 10 sequence are adjusted to be 01; for MSK modulation mode, the frequency offset is circularly shifted and adjusted, namely the original frequency shiftAdjust to->, wherein />Is the turnover adjustment quantity-> and />Respectively signal band enableLowest and highest frequencies permitted;

step S4, according to the authentication mark sequence obtained in the step S2, setting a section of spreading code corresponding to each element of the authentication mark sequence in a period of a public periodic spreading code, and in the first half or the second half of the public periodic spreading code of the navigation signal, wherein the first half or the second half is determined by the mark of the corresponding element of the authentication mark sequence, processing signal chips of the public periodic spreading code based on the processing position obtained in the step S3, and obtaining a processed mixed spreading code;

and S5, combining the processed mixed spread spectrum code obtained in the step S4 with the navigation message and the carrier wave to generate a navigation signal.

2. The method for generating civil anti-counterfeit navigation signals based on random processing of spread spectrum codes according to claim 1, wherein in said step S1, public key cryptosystem SM2 or ECDSA is used.

3. The method for generating civil anti-counterfeit navigation signals based on random processing of spreading codes according to claim 1, wherein in said step S2, a digital signature is modulated onto a basic authentication spreading code in a CSK modulation manner to obtain an authentication flag sequence.

4. The civil anti-fake navigation signal generating method based on the random processing of the spread spectrum code according to claim 3, wherein the mathematical expression of the anti-fake navigation signal is as follows by adopting a BPSK modulation mode:

，

wherein ,is signal power, +.>Is a navigation message, & lt + & gt>An authenticated and modified spreading code +.>Is the carrier frequency of the wave,the initial carrier phase j is an imaginary unit, t is signal time, and the anti-fake information is carried on the spread spectrum code of the navigation signal and broadcast to the user along with the navigation signal.

5. A civil anti-counterfeiting navigation signal receiving method based on spread spectrum code random processing, which is used for receiving a signal generated by the civil anti-counterfeiting navigation signal generating method based on spread spectrum code random processing according to any one of claims 1 to 4, and is characterized in that: the receiving method comprises two receiving processing modes of a slow channel and a fast channel.

6. The civil anti-counterfeiting navigation signal receiving method based on the random processing of the spread spectrum code according to claim 5, wherein in a slow channel processing mode, the method comprises the following steps:

step S61, the receiver captures and tracks the navigation signal, and the correlation value and the navigation message of the on-time branch are proposed from the tracking channel;

step S62, before the complete navigation message of an authentication period is received, the receiver firstly caches the adjacent difference result of the on-time branch related value as the observed quantity of the authentication mark sequence; after the navigation message of one authentication period is completely received, the receiver calculates the authentication mark spread spectrum code of the current authentication period from the navigation message through the derivation algorithm of the authentication mark spread spectrum code;

step S63, the receiver uses the authentication mark spread spectrum code of the authentication period and the cached authentication mark sequence observed quantity to carry out correlation calculation, and the digital signature carried in the digital signature is obtained through a CSK demodulation algorithm;

in step S64, the receiver uses the public key of the public asymmetric cryptosystem to verify the consistency of the navigation message and the digital signature, and obtains the result of the navigation signal authentication.

7. The civil anti-counterfeiting navigation signal receiving method based on the random processing of the spread spectrum codes according to claim 5, wherein in a fast channel processing mode, the steps are as follows:

step S71, the receiver acquires the authentication key and generates a spread spectrum code processing position according to the signal time, or receives the spread spectrum code processing position of the time period near the current moment;

step S72, according to the indication of the spreading code processing position, the receiver extracts the corresponding signal sampling observation, and carries out correlation operation with the signal sampling observation by using the processed spreading code;

in step S73, the receiver performs the hypothesis testing procedure of the authentication detector with the correlation operation result as the authentication detection amount, and obtains the result of the signal trusted authentication.