CN114124154B

CN114124154B - Frequency hopping synchronization method and system based on TOD

Info

Publication number: CN114124154B
Application number: CN202010893459.4A
Authority: CN
Inventors: 富尧; 钟一民; 余秋炜
Original assignee: Ruban Quantum Technology Co Ltd; Nanjing Ruban Quantum Technology Co Ltd
Current assignee: Ruban Quantum Technology Co Ltd; Nanjing Ruban Quantum Technology Co Ltd
Priority date: 2020-08-31
Filing date: 2020-08-31
Publication date: 2023-02-10
Anticipated expiration: 2040-08-31
Also published as: CN114124154A

Abstract

The invention provides a frequency hopping synchronization method and a frequency hopping synchronization system based on TOD, which improve a frequency hopping frequency generation method in the existing frequency hopping synchronization method based on TOD and comprise the following steps: the sender calculates the symmetric key between the sender and the receiver by using n different hash functions to obtain n hash values; a sender acquires TOD information of the current moment, takes TOD information of n-1 previous moments with the same step length, and then calculates a random code for the high-order content TODH of each TOD information; and finally, calculating n frequency hopping frequencies by using the corresponding TODH, the random code and the hash value in a combined operation mode. The invention converts TOD information into random codes which cannot be acquired by an enemy, simultaneously designs a unique frequency calculation method, and when the TODH is updated, n frequency hopping frequencies change along with the TOD information, and one frequency hopping frequency is only used in one period, thereby increasing the variability of the frequency hopping frequency, increasing the difficulty of the enemy in cracking the frequency hopping frequency, and improving the immunity and confidentiality in the frequency hopping synchronization process.

Description

Frequency hopping synchronization method and system based on TOD

Technical Field

The invention relates to the field of data chain systems, in particular to a frequency hopping synchronization method and system based on TOD.

Background

The frequency hopping refers to that the signal carrier waves do not hop continuously, so that the purpose that the carrier waves cannot be predicted by an enemy is achieved. The frequency hopping is divided into two steps of frequency hopping synchronization and frequency hopping data transmission. The frequency hopping synchronization means that both parties define the time point and the frequency hopping rule of frequency hopping, and the steps must be completed in advance before data transmission. There are about 4 major frequency hopping synchronization methods, the more important of which is the synchronization header method.

The current synchronization word method is generally a TOD-based synchronization word method, and the related principles of the existing TOD-based synchronization word method are mentioned in Simulink-based frequency hopping synchronization technology simulation platform design and implementation of [ D ] sinus silk, university of electronic technology, 2013 (01) ".

In the existing synchronization prefix method based on TOD, a sender and a receiver usually have the same symmetric key and frequency hopping frequency table, then the sender calculates a frequency hopping sequence according to TOD and the symmetric key, and controls the frequency hopping frequency table through the frequency hopping sequence to further control a local frequency synthesizer to generate frequency hopping frequency. In order to ensure that synchronization can be still achieved when the clocks of the transmitting and receiving parties have a certain difference, high-order information in the TOD information is usually extracted as TODH high-order (TODH), such as minute and high-order information thereof, and the system calculates the synchronization frequency according to the TODH instead of all TOD information, thereby ensuring that the same synchronization frequency still exists when the clocks of the transmitting and receiving parties have a certain difference. The remainder of TOD, except TODH, is used as TOD Low segment (TODL), which is a timing unit of the hop interval, and takes part in the calculation of the communication frequency but not in the calculation of the synchronization frequency.

In the TOD-based synchronization header method, the synchronization header structure mainly includes a correlation code portion and TODL information. The correlation code part is used for the receiving party to complete the acquisition of the synchronization frequency, and thus complete the correction of the high-segment content TODH in the local TOD of the receiving party. A complete correlation code is generally divided into n code sequences according to system requirements, and then transmitted on n hopping frequencies in a one-to-one correspondence manner, and one complete transmission of the correlation code is denoted as one correlation hop, and one correlation hop includes frequency f ₁ To f _n N hopping frequency hopping transmission of f ₁ To f _n Is the frequency hopping frequency set of the sync head. In order to increase the capturing probability of the synchronization frequency of the receiving party, usually multiple complete correlation codes are transmitted in one synchronization header structure, and then one synchronization header structure contains several correlation hops. The TODL information is positioned in the second half part of the synchronization header structure and is used for completing the correction of local TODL of the receiving party so as to realize synchronous tracking of the receiving party. To improve the security of the synchronization header, the TODL information is also typically divided into n segments to be transmitted on n hopping frequencies, with only a portion of the TODL content being transmitted on each frequency.

In the conventional TOD-based sync header method, in order to improve the interference immunity of sync header frequencies, these frequencies change with time: and if the TODH is updated once every time T, updating one frequency in the frequency hopping frequency set every time the TODH is updated once, so that all the frequencies in the frequency hopping frequency set are updated once after the time length nT.

However, although the existing TOD-based synchronous header method has a certain degree of immunity and confidentiality, the following defects still exist:

1. in the existing TOD-based synchronization prefix method, frequency hopping frequency is obtained by directly carrying out frequency conversion on TODH (high-order information) based on TOD (time of flight), and the calculated frequency hopping frequency is easy to crack by enemies because the TODH is easy to be obtained by the enemies; on the other hand, the frequency-concentrated frequency hopping frequency of the synchronization head is updated slowly, and only one frequency in the frequency set is updated every time the TODH is updated, which inevitably causes most of the frequencies to be used for many times, and the frequencies are easily captured by an enemy in the process of multiple use, thereby causing the synchronization head to be easily stolen or interfered by the enemy;

2. in the existing TOD-based synchronous header method, a symmetric key shared by a transmitting and receiving end is usually a pseudo-random number, a calculated frequency hopping sequence is also a pseudo-random number, and the pseudo-random number has predictability, so that the safety in the frequency hopping process is low, and quantum computation resistance cannot be realized;

3. in the TOD-based synchronous header method in the prior art, TODL is not protected by encryption and is easy to steal.

Disclosure of Invention

The purpose of the invention is as follows: in order to overcome the defects of the prior art, the invention provides a frequency hopping synchronization method and a frequency hopping synchronization system based on TOD.

The invention content is as follows: in order to overcome the problem that the frequency hopping frequency and TOD information are easy to crack in the existing synchronization prefix method based on TOD, the invention provides a frequency hopping synchronization method based on TOD, which improves the frequency hopping frequency generation method in the frequency hopping synchronization method, if n frequency hopping is needed for transmitting the synchronization sequence according to the requirement, the method for generating n frequency hopping frequencies for sending the synchronization sequence by a sender comprises the following steps:

the sender calculates the symmetric key between the sender and the receiver by using n different hash functions to obtain n hash values;

a sender acquires TOD information at the current moment, and takes the TOD information at n-1 previous moments with the same step length to count n TOD information; then, calculating a random code consisting of true random numbers according to the TODH of the high-order content of each TOD information to obtain n random codes in total;

and (3) calculating n frequency hopping frequencies by using the corresponding TODH, random codes and hash value in a combined operation mode:

wherein, f _i Representing the ith frequency hopping frequency generated by the sender at the current time, F representing a joint operation function, TODH (t) representing the high-segment content of the local TOD information of the sender at the time t, RF (t) representing a random code corresponding to the TODH (t), R _i Representing the ith hash value.

In the invention, on one hand, TODH which is easy to be obtained by an enemy is converted into a random code consisting of true random numbers, and then the random code is used for calculating frequency hopping frequency, so that TOD information obtained by the enemy becomes useless information. On the other hand, a unique frequency calculation method is designed, the frequency hopping frequency is calculated by combining hash values calculated by the TODH, the random code and the symmetric key, and when the TODH is updated, n frequency hopping frequencies change along with the change of the frequency hopping frequency, one frequency hopping frequency is only used in one period.

For the TOD-based frequency hopping synchronization method, several alternatives are provided below, but not as an additional limitation to the above general scheme, but only as a further supplement or preference, and each alternative can be combined separately for the above general scheme or be combined among multiple alternatives without technical or logical contradictions.

Optionally, the specific step of the receiver correcting the local TOD includes:

the receiver calculates at least one scanning frequency group, wherein one scanning frequency group comprises n scanning frequencies, and each scanning frequency is calculated by the receiver by adopting the same calculation method as the sender based on the local TOD information;

the receiving party scans the frequency in the synchronous sequence on each scanning frequency group until the frequency synchronous with the sending party is captured;

the receiver corrects the high-order content of the local TOD information according to the difference between the two synchronous frequency indexes;

after correcting the high-order content of the local TOD information, the receiving party recalculates the synchronous frequency, performs synchronous following jump on the synchronous frequency, receives the low-order content TODL of the TOD information of the transmitting party in the synchronous sequence, corrects the low-order content of the local TOD information according to the TODL, and realizes synchronization.

Optionally, before the sender sends the synchronization sequence, the TODL is encrypted by using a method agreed in advance with the receiver, and when the receiver receives the TODL of the sender, the TODL of the sender is obtained by decrypting the TODL by using the agreed method.

Optionally, the encryption manner for encrypting the TODL is as follows: the transmitting end uses the random code corresponding to the TODH of the current time to generate an encryption key, and uses the generated encryption key to encrypt TODL.

Optionally, the random code is obtained by the following method:

encrypting the TODH by using a symmetric key to obtain an initial position pointer of the random code;

calculating a step length for each bit of the random code by using a symmetric key and a TODH (time of flight data) combined calculation;

the initial position pointer and the step length of the first bit of the random code are jointly calculated to obtain an extraction pointer of the first bit of the random code; the extraction pointer of the first bit of the random code and the step length of the second bit of the random code are jointly calculated to obtain the extraction pointer of the second bit of the random code, and the extraction pointer of each bit of the random code is calculated by analogy;

and extracting corresponding key data of each bit from a symmetric key pool which is pre-stored in the local according to the extraction pointer to obtain a random code.

Optionally, the symmetric key between the sender and the receiver is obtained by the following method:

the method comprises the steps that a sender and a receiver apply for a public key and a private key of a user side to a key issuing server in advance before frequency hopping synchronization;

the key issuing server distributes a unique ID for the user side according to user application, then adopts a first hash function to map the client side ID to a user side public key, then calculates a user private key by using a system private key and the user public key of the key issuing server, and finally issues the calculated user private key and the user ID to the user side;

the sender and the receiver store the same symmetric key calculation function and the first hash function, when the symmetric key of the other party is calculated, the ID of the other party is calculated by using the first hash function to obtain the public key of the other party, and then the private key of the sender and the public key of the other party are subjected to combined calculation by using the symmetric key calculation function to obtain the symmetric key.

Optionally, the method further comprises the steps of:

the method comprises the steps that key fobs are locally configured on a sender and a receiver and used for storing a symmetric key pool and various functions used in the process of calculating frequency hopping frequency, and a TPM/TCM chip resistant to disassembly is also deployed in each key fob and used for storing public and private keys of a user;

and a TPM/TCM chip which is resistant to disassembly is locally deployed at the key issuing server and is used for storing the public and private keys of the system.

The invention also provides a frequency hopping synchronization system based on TOD, the system comprises a sender and a receiver, and the sender and the receiver adopt the method to carry out frequency hopping synchronization.

Has the beneficial effects that:

1. in the invention, TOD information is converted into random codes which cannot be acquired by an enemy, so that the TOD information acquired by the enemy becomes useless information, meanwhile, a unique frequency calculation method is designed, the frequency hopping frequency is calculated by combining hash values calculated by using the TODH, the random codes and a symmetric key, and n frequency hopping frequencies change along with the change of the TODH every time, and one frequency hopping frequency is only used in one period.

2. The invention adopts the symmetric key and the TODH to calculate the random code consisting of the true random numbers, the true random numbers have unpredictability, and the true random numbers adopt different step lengths to take out a plurality of random number bits one by one from the key pool, the step lengths are different each time, the difficulty of the cracking of the enemy is greatly increased, and the quantum computation resistant communication between the sender and the receiver can be realized.

3. In the invention, TODL is encrypted and protected and is not easy to steal.

Drawings

FIG. 1 is a TOD-based synchronous prefix sequence format diagram;

fig. 2 is an exemplary diagram of a process of acquiring a random code involved in the present invention.

Detailed Description

The invention will be further described with reference to the accompanying drawings and specific embodiments. It is to be understood that the present invention may be embodied in various forms, and that there is no intention to limit the invention to the specific embodiments illustrated, but on the contrary, the intention is to cover some exemplary and non-limiting embodiments shown in the attached drawings and described below.

It is to be understood that the features listed above for the different embodiments may be combined with each other to form further embodiments within the scope of the invention, where technically feasible. Furthermore, the particular examples and embodiments of the invention described are non-limiting, and modifications may be made in the structure, steps, sequence of steps, or illustrated above without departing from the scope of the invention.

The invention aims to solve the problem that in the existing frequency hopping synchronization method based on TOD, a synchronization head is easy to attack, so that the safety in the frequency hopping synchronization process is not high. In view of this, the present invention provides a frequency hopping synchronization method and system based on TOD. This will be further illustrated by the specific examples below.

The embodiment is as follows:

the frequency hopping synchronization method based on TOD information is realized on a sender and a receiver. In this embodiment, a sender is set as a, and a receiver is set as B. The sender and the receiver are both provided with key fobs, and the key fobs store symmetric key pools, namely, the key pools of the sender and the receiver are equal. The key fob also stores public and private key parameters based on ID cryptography, and is issued by a key issuing server, and the specific steps are as follows:

the key issuing server firstly needs to establish a set of system parameters based on ID key science, and the steps are as follows:

(1) Let q be a large prime number, generate G ₁ And G ₂ ，G ₁ And G ₂ Q-order addition cycle groups and multiplication cycle groups, respectively. Mapping

Into a bilinear map. Random selection of G ₁ The generator P of (2);

(2) Defining a hash function H: {0,1} ^* →G ₁ ^* ；

(3) Setting other system parameters ad _ paras;

(4) Randomly taking s ∈ Z _q ^* As a system private key of the algorithm, s is only stored in a key issuing server KS, and a system public key P is calculated _pub ＝s·P。

The algorithm parameters are

The key issuing server stores the system parameters based on the ID key science, and is used for generating a system public key, a system private key, IDs of requesters (sender and receiver), a public key and a private key.

Taking sender a and receiver B as an example:

when the key issuing server issues a public and private key for a sender A, a unique code is generated as an ID _A Then calls the hash function H ₁ Computing public key PK _A ＝H(ID _A ) Then according to the public key PK _A Computing the private Key SK _A ＝s*PK _A . The receiver B calculates ID by the key issuing server _B Public key PK _B ＝H(ID _B ) Private key SK _B ＝s*PK _B . The key issuing server then sends the ID _A 、SK _A Key fob issued to sender A, ID _B 、SK _B A key fob issued to recipient B;

the sender A can calculate the symmetric key with the receiver B

The receiver B can calculate the symmetric key with the sender A

From ID cryptography:

in the above scheme, the system private key s and the system public key P _pub The TPM/TCM chip is stored locally in the key issuing server, the TPM/TCM chip which is resistant to disassembly can be deployed locally in the key issuing server, and the system master key and the system public key are stored in the chip. The private key and system public key of the terminal are also stored in the built-in TPM/TCM chip of the terminal key fob. The security chip has the function of anti-disassembly, and the enemy cannot obtain the data in the chip. Even if the key fob is lost and cracked, an enemy can only obtain the ID and the hash function H to further calculate the public key of the terminal, and cannot obtain the symmetric key on the premise of not obtaining the terminal private key and the system master key, and meanwhile, the enemy cannot obtain the system private key due to the fact that the enemy cannot obtain the system public key, and quantum computation resistance is achieved.

In addition, the key fob also stores an array of hash functions,is expressed as { H ₁ ,H ₂ ,H ₃ ,……,H _N }。

After the sender and the receiver successfully acquire the public and private keys of the user, the frequency hopping synchronization is started, and the whole process is as follows:

s1, a sender generates a synchronization sequence and a hopping frequency for sending the synchronization sequence, and the structure of the synchronization sequence is shown in fig. 1, and includes a correlation code portion (a preamble sequence and the synchronization sequence), a lower content TODL in a local TOD at the current time of the sender, and a network number. The correlation code part is divided into n code sequences and transmitted in a correlation hop, one correlation hop comprises n hopping frequencies, and the n hopping frequencies are generated as follows:

1.1. assuming that the number of hopping frequencies of one relevant hop is 5, the current time is t ₀ Taking the step length as t (t is the sending end local clock updating period), obtaining the TODH of the previous 4 moments, and then 5 TODH (TODH (t) together with the TODH of the current moment in total ₀ )、TODH(t ₀ -t)、TODH(t ₀ -2t)、TODH(t ₀ -3t)、TODH(t ₀ -4 t)), the frequency numbers of the respective frequencies are referred to as frequency 1 to frequency 5 in order; each frequency number corresponds to a code sequence, referred to in order as code sequence 1 to code sequence 5.

Sender A based on ID of receiver B _B Calculating to obtain a symmetric key K _AB Then take five hash functions { H } from the hash array ₁ ,H ₂ ,H ₃ ,H ₄ ,H ₅ H, using five hash functions to sequentially pair K _AB Calculating to obtain five Hash values { R ₁ ,R ₂ ,R ₃ ,R ₄ ,R ₅ }。

1.2. Each correlation hop has 5 frequencies, each frequency corresponds to one TODH, the sender calculates one random code RF for each TODH, the calculation process is shown in fig. 2, and the method includes the following steps:

calculating to obtain an initial position pointer PRF = F of the random code RF _PRF (TODH||K _AB ) mod KPL, where mod represents the modulo operation, KPL is the key pool size, i.e., the total number of bits, and PRF is a pointer pointing to a location in the key pool. Set the required length of RFThe degree is N bits, and the step length is calculated in sequence: LRF ₁ ＝F _LRF (TODH||K _AB )，LRF ₂ ＝F _LRF (LRF ₁ ||TODH||K _AB )，LRF ₃ ＝F _LRF (LRF ₂ ||TODH||K _AB )，…，LRF _N ＝F _LRF (LRF _N-1 ||TODH||K _AB ). Function F _PRF () And F _LRF () Is an arbitrarily specified function. Then sequentially calculating the pointers PRF for extracting the random code ₁ ＝PRF+LRF ₁ mod KPL，PRF ₂ ＝PRF ₁ +LRF ₂ mod KPL，…，PRF _N ＝PRF _N-1 +LRF _N mod KPL。PRF ₁ Pointing to the starting position of the random code RF, i.e. the position of the first bit, PRF ₂ Pointing to the position of the second bit of the random code RF and so on. According to PRF ₁ 、PRF ₂ 、…、PRF _N And sequentially taking out the key data of N bits at the corresponding positions from the key pool. And if the key pool size KPL is exceeded, returning to the key pool head by utilizing a mode of taking a module of the KPL.

In the prior art, there are two main methods for obtaining a key from a key pool: the first method is to directly extract the key seed ID in a key pool, and the key seed ID in the method is in one-to-one correspondence with the key; the second is to select a location and then obtain the entire key for that location. With a total length of 2 ³⁰ bit, the key length is 2 ¹⁰ bit is taken as an example, the number of keys usable by the first method is 2 ²⁰ The number of usable keys in the second method is 2 ³⁰ And the updating of the key pool is required to be carried out in a short time period. In the patent, the key is selected from the key pool by calculating a step size for each bit of data in the key, and the number of usable keys is 2 ¹⁰²⁴ And (4) respectively. The method improves the utilization rate of the secret key, reduces the times of supplementing the secret key by the user, reduces the maintenance cost of the user and ensures that the symmetric secret key pool is more convenient to use.

1.3. After the random code is calculated, the frequency hopping frequencies are calculated, each TODH corresponds to one frequency hopping frequency, so 5 TODHs calculate 5 frequencies, each frequency is determined by 3 parameters, that is: TODH, RF and R.

In the present embodiment, only two ways of calculating the frequency are proposed, but other methods of calculating the frequency based on the above 3 parameters should also be included in the scope of the present invention.

The method comprises the following steps: calculating the fundamental frequency f by a synchronous frequency calculation formula _si ＝F _f (TODH(t ₀ -(i-1)t),RF(t ₀ - (i-1) t)), i =1,2, \ 8230;, 5, wherein F _f () The function is calculated for the synchronization frequency designed according to the requirements. Then, offset calculation is carried out on the basic frequency to obtain the synchronous frequency f _i ＝f _si +c*R _i Wherein c is such that f _i Coefficient falling within a reasonable frequency range, R _i The hash value calculated in step 1.

The method 2 comprises the following steps:

directly calculated by a synchronous frequency algorithm

Suppose f is calculated using method 1 ₁ To f ₅ F calculated by the sender at different times ₁ To f ₅ The values are as follows:

time t ₀ ：

Time t ₀ +t：

Time t ₀ +2t：

Time t ₀ +3t：

Time t ₀ +4t：

From above f ₁ To f ₅ Can be seen from the expression of (A), since R is considered when calculating the frequency _i The 5 frequencies are different at different times, and each time the TODH changes, the 5 frequencies change.

1.4. Using the random code RF taken out corresponding to the TODH at the current time, and generating an algorithm F through a secret key _L () Calculated to yield KL = F _L (RF). And after the TOD information low-segment TODL is encrypted by using KL, the synchronization sequence is sent to a receiving party.

S2, a receiving party captures a synchronous frequency through frequency scanning, receives a synchronous sequence on the synchronous frequency, and corrects local TOD by using the received synchronous sequence, and the method comprises the following specific steps:

2.1. the receiving side receives the synchronous sequence, and the current TOD high segment of the receiving side is TODH '(t' ₀ ) On the receiving side, the TOD high segment TODH ' (t ') of the first 4 time instants is taken at time intervals of t ' ₀ -t)、TODH′(t′ ₀ -2t)、TODH(t′ ₀ -3t)、TODH′(t′ ₀ 4 t), the random codes corresponding to 5 TODH values are respectively: RF '(t' ₀ )、RF′(t′ ₀ -t)、RF′(t′ ₀ -2t)、RF(t′ ₀ -3t)、RF′(t′ ₀ -4 t). The sending end calculates the symmetric key, and then calculates R according to the symmetric key ₁ To R ₅ 。

2.2. Scan frequency group generation

We are based on TODH '(t' ₀ ) Generating 5 frequencies as scan frequency group 1 based on TODH '(t' ₀ T) generates 5 frequencies as swept frequency group 2, and so on, generates 5 swept frequency groups for a total of 25 swept frequencies. The method comprises the following specific steps:

frequency group 1:

frequency group 2:

frequency group 3:

frequency group 4:

frequency group 5:

2.3. the receiver performs a slow scan on the five frequencies of the sender through the five frequency groups. The slow scan type results are as follows:

suppose now that the sender is at t ₀ The 5 frequencies are transmitted, since in our scheme the frequencies are related to 3 parameters, the following form is written:

TODH(t ₀ ),RF(t ₀ ),R ₁ →f ₁

TODH(t ₀ -t),RF(t ₀ -t),R ₂ →f ₂

TODH(t ₀ -2t),RF(t ₀ -2t),R ₃ →f ₃

TODH(t ₀ -3t),RF(t ₀ -3t),R ₄ →f ₄

TODH(t ₀ -4t),RF(t ₀ -4t),R ₅ →f ₅

receiver is at t' ₀ The 5 sweep frequency groups are generated as follows:

frequency group 1:

frequency group 2:

frequency group 3:

frequency group 4:

frequency group 5:

because we have R inside the frequency ₁ To R ₅ Is therefore f' ₁ 、f′ ₆ 、f′ ₁₁ 、f′ ₁₆ 、f′ ₂₁ Dematching f ₁ From f' ₂ 、f′ ₇ 、f′ ₁₂ 、f′ ₁₇ 、f′ ₂₂ Dematching f ₂ And so on.

Suppose TODH '(t' ₀ ) And TODH (t) ₀ ) If equal, then with set 1, scan to get f' ₁ ＝f ₁ At this time, it means that the high segment of the receiving local TOD coincides with the high segment of the transmitting local TOD.

If TODH '(t' ₀ -t) and TODH (t) ₀ ) Equal, then when swept with set 1, all frequencies within set 1 are found to be mismatched, f 'in set 2' ₆ ＝f ₁ F 'in group 3' ₁₂ ＝f ₂ F 'in group 4' ₁₈ ＝f ₃ F 'in group 5' ₂₄ ＝f ₄ . Then the high segment of the local TOD of the receiver lags the high segment of the local TOD of the sender by a time difference of t, the high segment of the local TOD of the receiver is corrected at this time to realize synchronization and jump, and the receiver receives the synchronization sequence at the synchronization frequency.

2.3. The receiver calculates the corresponding random code RF according to the above-mentioned method by using the updated local TOD high-segment TODH ″ ₀ ". Using a key generation algorithm F _L () KL' = is obtained through calculationF _L (RF ₀ "). And the receiver decrypts the TODL information in the synchronous sequence by utilizing the KL' to obtain the TODL of the sender, and corrects the low segment of the local TOD of the receiver according to the TODL of the receiver to finish frequency hopping synchronization.

The technical features of the embodiments described above may be arbitrarily combined, and for the sake of brevity, all possible combinations of the technical features in the embodiments described above are not described, but should be considered as being within the scope of the present specification as long as there is no contradiction between the combinations of the technical features.

The above-mentioned embodiments only express several embodiments of the present invention, and the description thereof is more specific and detailed, but not construed as limiting the scope of the invention. It should be noted that, for a person skilled in the art, several variations and modifications can be made without departing from the inventive concept, which falls within the scope of the present invention. Therefore, the protection scope of the present patent should be subject to the appended claims.

Claims

1. A frequency hopping synchronization method based on TOD comprises the following steps: a sender generates a frequency hopping frequency and a synchronization sequence, then sends the synchronization sequence on the frequency hopping frequency, a receiver captures the synchronization frequency through frequency scanning, receives the synchronization sequence on the synchronization frequency, and corrects local TOD by using the received synchronization sequence; the method is characterized in that:

the method for generating n hopping frequencies for transmitting the synchronization sequence by the transmitting side comprises the following steps:

a sender acquires TOD information at the current moment, and acquires the TOD information at n-1 previous moments by the same step length to count n TOD information; then, calculating a random code for the TODH of the high-order content of each TOD information to obtain n random codes in total;

and (3) calculating n frequency hopping frequencies by using the corresponding TODH, random code and hash value joint operation:

f ₁ ＝F(TODH(t ₀ ),RF(t ₀ ),R ₁ )

f ₂ ＝F(TODH(t ₀ -t),RF(t ₀ -t),R ₂ )

f _n ＝F(TODH(t ₀ -(n-1)t),RF(t ₀ -(n-1)t),R _n )

wherein f is _i Represents the ith frequency hopping frequency generated by the sender at the current moment, F represents a joint operation function, TODH (t) represents the high-segment content of the local TOD information of the sender at the moment t, RF (t) represents a random code corresponding to the TODH (t), R _i Representing the ith hash value.

2. The TOD-based frequency hopping synchronization method according to claim 1, wherein the step of modifying the local TOD at the receiving end comprises:

the receiving party scans the frequency in the synchronous sequence on each scanning frequency group until the synchronous frequency of the sending party and the receiving party is captured;

3. The TOD-based frequency hopping synchronization method according to claim 2, wherein the TODL is encrypted by the sender in a pre-defined manner with the receiver before the sender transmits the synchronization sequence, and the TODL of the sender is obtained by the receiver decrypting the TODL in the pre-defined manner when the receiver receives the TODL of the sender.

4. The TOD-based frequency hopping synchronization method according to claim 3, wherein the encryption method for encrypting TODL is as follows:

the transmitting end uses the random code corresponding to the TODH of the current time to generate an encryption key, and uses the generated encryption key to encrypt TODL.

5. The TOD-based frequency hopping synchronization method according to any one of claims 1 to 4, wherein the random code is obtained by:

the initial position pointer and the step length of the first bit of the random code are used for joint calculation to obtain an extraction pointer of the first bit of the random code; the extraction pointer of the first bit of the random code and the step length of the second bit of the random code are jointly calculated to obtain the extraction pointer of the second bit of the random code, and the extraction pointer of each bit of the random code is calculated by analogy;

and extracting corresponding each bit of key data from a symmetric key pool which is stored locally in advance according to the extraction pointer to obtain the random code.

6. The TOD-based frequency hopping synchronization method according to claim 5, wherein said symmetric key between said sender and receiver is obtained by the following method:

a sender and a receiver apply for a public and private key of a user side to a key issuing server in advance before frequency hopping synchronization;

7. The TOD-based frequency hopping synchronization method according to claim 6, further comprising the steps of:

8. A TOD-based frequency hopping synchronization system, wherein the system comprises a sender and a receiver, and the sender and the receiver perform frequency hopping synchronization by using the method of any one of claims 1 to 6.