Physical layer authentication mechanism for the Internet of Things and watermark update method based on one-way hash chain

Abstract

The present invention discloses a physical layer authentication mechanism applicable to the Internet of Things and a watermark update method based on a one-way hash chain. By adopting a spread spectrum code watermark authentication method, the Internet of Things terminal can realize low-complexity message authentication at the physical layer, thereby improving the authentication efficiency and security of the system; by improving the correlation value judgment strategy of the existing spread spectrum code watermark authentication scheme at the receiving end, the low-cost terminal can distinguish between valid frames and invalid frames without relying on high-precision channel estimation, thereby improving the flexibility and applicability of the authentication scheme; by introducing a one-way hash chain as a watermark update scheme, the resistance of the device to replay attacks is enhanced; in addition, in response to the problem of limited length of the one-way hash chain, the present invention designs a scheme that can regenerate and update the hash chain without restarting the upper-layer protocol authentication process, so that the physical layer authentication can be continuously and smoothly executed for a long time.

Description

Technical Field

[0001] The present invention relates to the field of physical layer security technology for the Internet of Things, and more specifically, to a physical layer authentication mechanism applicable to the Internet of Things and a watermark update method based on a one-way hash chain. Background Art

[0002] Identity authentication is a crucial component of IoT security. Its purpose is to verify the legitimacy of terminal identities, thereby preventing potentially malicious terminals from accessing the network. In recent years, physical layer authentication, as a security technology with unique advantages, has been gaining increasing attention from academia and industry. The core concept of physical layer authentication is to verify the legitimacy of the sender by extracting and judging the physical layer features or physical layer tags of the transmitted signal, while preventing potential attackers from obtaining the correct feature or tag information. Compared to traditional authentication strategies used in the upper layers of the communication protocol stack, physical layer authentication offers several advantages in IoT applications: low computational complexity, good compatibility, and the ability to provide information-theoretic security assurance.

[0003] In their 2008 paper "Physical-Layer Authentication," Paul L. Yu et al. from the University of Maryland proposed a classic physical-layer tag superposition and authentication scheme. In this method, an authentication tag is disguised as noise and superimposed on a message symbol. Various tag superposition and authentication schemes derived from this classic authentication scheme offer the advantages of low computational complexity and strong tag concealment. However, the authentication tag superimposed on the message symbol can, to a certain extent, reduce the signal-to-noise ratio of the data and increase the bit error rate, thereby reducing the availability of the data portion. Furthermore, some low-cost IoT terminals can only provide limited channel estimation accuracy due to hardware and power consumption limitations. Many physical-layer tag superposition schemes often assume that the terminal can perfectly estimate the channel state, which limits their application in low-cost IoT terminals.

[0004] The spread spectrum code watermark authentication scheme was originally proposed by American GPS expert Logan Scott in his 2003 paper "Anti-spoofing and authenticated signal architectures for civil navigation systems", and has attracted the attention of the Global Navigation Satellite System (GNSS) community in recent years. In this scheme, the sender replaces part of the signal's spread spectrum code with a "watermark" sequence, and the receiver authenticates the signal by correlating this part of the code. The application of this scheme in GNSS has the advantages of fast authentication speed and good anti-counterfeiting attack performance. The present invention applies the basic concept of spread spectrum code authentication to IoT communications, and further designs and improves the receiver's authentication process based on the characteristics of low-cost terminals to meet the requirements of low computational complexity of IoT terminals.

[0005] The one-way hash chain method, originally proposed by American mathematician Lamport, is widely used in various cryptographic systems due to its one-way nature and high computational efficiency. In the 2015 paper "Physical Layer Spectrum Usage Authentication in Cognitive Radio: Analysis and Implementation," published by Kapil M. Borle et al. of Syracuse University, and the 2020 paper "Physical-Layer Authentication for Internet of Things via WFRFT-Based Gaussian Tag Embedding," published by Ning Zhang et al. of the University of Windsor, Canada, one-way hash chains were combined with updates to physical layer authentication tag parameters, making the authentication system resistant to replay attacks. However, these two works did not consider the issue of hash chain regeneration after exhaustion. If the hash chain regeneration requires the use of an upper-layer authentication protocol to distribute the tail node of the hash chain, as is done during initial system startup, this would incur additional computational overhead for IoT terminals and reduce the hash chain's efficiency. Summary of the Invention

[0006] The present invention provides a physical layer authentication mechanism applicable to the Internet of Things and a watermark update method based on a one-way hash chain, which solves the problem that the regeneration of the hash chain after exhaustion is not taken into account, resulting in additional computing overhead of the Internet of Things terminal and reduced utilization efficiency of the hash chain.

[0007] In order to solve the above technical problems, the technical solutions of the present invention are as follows:

[0008] A physical layer authentication mechanism applicable to the Internet of Things and a watermark update method based on a one-way hash chain, comprising the following steps:

[0009] S1: Before starting message transmission, the legitimate sender generates a random number and generates a hash chain by processing the random number;

[0010] S2: The legitimate sender and the legitimate receiver establish a shared symmetric key through upper-layer protocol authentication, and the legitimate sender sends the tail node of the hash chain to the legitimate receiver;

[0011] S3: During the message transmission phase, the legitimate sender generates an authentication tag based on the shared symmetric key and the message code element of the payload portion of the physical frame in each frame transmission period, and generates a first replacement position index set based on the authentication tag;

[0012] S4: The legitimate sender selects the corresponding node on the hash chain and replaces the chip at the position corresponding to the chip replacement position index set in the preamble chip sequence in the physical frame with the watermark sequence corresponding to the node. When the hash chain node of the legitimate sender is exhausted, the legitimate sender regenerates a new hash chain and puts the tail node of the new hash chain in the message frame generated by the watermark sequence using the head node of the old hash chain and sends it to the legitimate receiver;

[0013] S5: After the legal receiver detects the physical frame, it generates a label based on the shared symmetric key and the demodulated message codewords and obtains a second replacement index set;

[0014] S6: The legitimate receiver locates the received signal at the chip replacement position corresponding to the physical frame using the second replacement index set, and searches for the watermark sequence with the highest correlation value with the received signal in the watermark sequence set using a correlation energy detection method. The watermark sequence set is preset on the legitimate receiver.

[0015] S7: The legitimate receiver uses the watermark sequence with the highest correlation value with the received signal and the corresponding preamble reference signal at the position of the corresponding code chip replacement in the physical frame to perform matched filtering on the received signal and obtain a statistical check value. If the statistical check value is less than 0, the legitimate receiver determines that the received signal is illegal and discards it. If the statistical check value is greater than 0, the process proceeds to step S8;

[0016] S8: The legal receiver uses the watermark sequence with the highest correlation value with the received signal to restore the corresponding hash node, and obtains the calculation result after several operations. The calculation result is then compared with the last hash node that passed the verification. If the two are equal, the legal receiver determines that the received signal is legal and the hash node passes the verification; if the two are not equal, the receiver determines that the received signal is illegal and discards it.

[0017] Furthermore, the random number x in step S1 is concatenated, hashed, and truncated K+1 times continuously to generate a hash chain H with a length of K+1. K →H K-1 →…→H0, specifically:

[0018] S1.1: The sender generates a random number x as a starting seed and selects a hash function h(·) that can output an M-bit binary sequence;

[0019] S1.2: Use the hash function h(·) and the random number x to generate the sequence h(x), and truncate h(x) to get the head node H of the hash chain. K :

[0020]

[0021] Where, From position u K Start by intercepting log2W bits of the sequence h(x) and use i K Indicates that node H is expected to be used K The frame period index is u K = K mod(-log2W), W is the size of the watermark sequence set;

[0022] S1.3: Based on the generated node H j , computing node H j-1 :

[0023]

[0024] Where H j ‖i j Indicates that node H j and the expected use of node H j Frame period index i j The sequence obtained by splicing, i j = j-1 mod(-log2W), j=1,2,...,;

[0025] S1.4: After repeating step S1.3 K times, the legitimate sender finally generates a one-way hash chain H with a length of K+1. K →H K-1 →…→H0.

[0026] Furthermore, in step S2, the legitimate sender and the legitimate receiver establish a shared symmetric key k through upper layer protocol authentication, and the legitimate sender sends the tail node H0 of the hash chain to the legitimate receiver.

[0027] Furthermore, in step S3, the legitimate sender generates an authentication tag t according to the shared key k and the message code element of the physical frame payload in the i-th frame transmission cycle. i , and according to the certification label t i Generate the first replacement position index set Specifically:

[0028] The legitimate sender generates the message code element m in the physical frame payload part during the i-th frame transmission cycle. i , using hash function g(·,·) to generate authentication tag t i :

[0029] t i =g(m i ,k)

[0030] Generate an initial replacement position indication sequence z0 = [1, 1, 1, ..., 0, 0, ..., 0], the length of the initial replacement position indication sequence z0 is L, the values ​​of the first N elements are all 1, and the values ​​of the remaining elements are 0, and t i After setting it as the seed of the pseudo-random number generator, the Knuth-Durstenfeld shuffling algorithm is used to shuffle the cards to obtain the corresponding z i , sequence z i The set of element subscripts with a median value of 1 is the first replacement position index set

[0031] Further, step S4 specifically includes:

[0032] When the legitimate sender selects the corresponding node on the hash chain, the hash chain is used in reverse, specifically:

[0033] Let the period index of the legitimate sender sending the message to be authenticated for the first time be t. At this time, the legitimate sender should use the watermark sequence corresponding to node H1 to replace the preamble code chip. At the next period t+1, the sender uses the watermark sequence corresponding to H2 to replace the preamble code chip. Similarly, at period t+k, the sender should use H k+1 The corresponding watermark sequence replaces the preamble code chips;

[0034] In step S4, the chip at the position corresponding to the chip replacement position index set in the preamble chip sequence in the physical frame is replaced with the watermark sequence corresponding to the node, specifically:

[0035] Let the original unwatermarked preamble code sequence be expressed as p = [p1, p2, ..., p L ],p k ∈{-1,1}, the sender needs to replace part of the code chips in p with the watermark sequence s=[s1,s2,…,sN ],s k ∈{-1,1}, the replacement rule can be expressed as follows:

[0036]

[0037] Where,

[0038] Furthermore, in step S4, when the hash chain nodes of the legitimate sender are exhausted, the legitimate sender regenerates a new hash chain and places the tail node of the new hash chain in a message frame that generates a watermark sequence using the head node of the old hash chain and sends it to the legitimate receiver. Specifically,

[0039] S4.1: The legitimate sender regenerates a new seed value x′ and generates a new hash chain of length K+1: H′ according to steps S1.2 to S1.4. K →H′ K-1 →…→H′0;

[0040] S4.2: In the i K In a cycle, the legitimate sender puts the new tail node H′0 in the message to be sent in this cycle, and uses H K The corresponding watermark sequence watermarks the signal;

[0041] S4.3: The legal recipient is in the i K The corresponding signal is received in a cycle, and the legitimacy of the signal is verified to obtain the tail node H′0 of the new hash chain;

[0042] S4.4: The old hash chain is exhausted, and then the new hash chain H′ is generated. K →H′ K-1 →…→H′0 is put into use, and when the new hash chain is about to be exhausted, the legitimate sender and the legitimate receiver continue to generate a new hash chain for use in the manner of steps S4.1 to S4.3.

[0043] Further, in step S5, after the legal receiver detects the physical frame, it despreads and demodulates the payload portion to obtain And use the hash function g(·,·) to generate the authentication tag Generate an initial replacement position indicator sequence The initial replacement position indication sequence The length is L, the first N elements have the value 1, and the rest have the value 0. After setting it as the seed of the pseudo-random number generator, the Knuth-Durstenfeld shuffling algorithm is used to shuffle the cards to obtain the corresponding sequence The set of element subscripts with a median value of 1 is the second replacement position index set I′.

[0044] Furthermore, in step S6, the legitimate receiver locates the received signal r at the corresponding chip replacement position of the physical frame through the second replacement index set I′. i , and detect the watermark sequence using the correlation energy detection method Search out and receive signal r i The watermark sequence with the highest correlation value

[0045]

[0046] Furthermore, in step S7, the legitimate receiver uses the watermark sequence with the highest correlation value with the received signal. The preamble reference signal p at the second replacement position index set I′ corresponding to the physical frame I′ and the received signal r i Perform matched filtering and obtain the statistical test value τ i :

[0047]

[0048] If τ i <0, the legal receiver determines the received signal as illegal and discards it. i >0, then go to step S8.

[0049] Furthermore, in step S8, the legitimate receiver uses the watermark sequence with the highest correlation value with the received signal Restore the corresponding hash node Let the last verified hash node value be recorded as And order Represents a hash node Perform k consecutive splicing, hashing, and truncating operations to generate hash nodes. After ij splicing, hashing, and truncating operations, we get Compare and If the value of The legal receiver determines that the received signal is legal if The legal receiver then determines that the received signal is illegally discarded.

[0050] Compared with the prior art, the beneficial effects of the technical solution of the present invention are:

[0051] In the first stage of authentication, this invention introduces a method similar to envelope detection and non-coherent demodulation, enabling legitimate receivers to distinguish valid frames from legitimate senders from invalid frames from unregistered terminals without relying on channel estimation. By combining hypothesis testing and one-way hash chain verification, legitimate receivers can simultaneously filter valid frames and resist replay attacks. By employing a simple hash chain regeneration method, signaling interactions, upper-layer protocol processes, and public key computation required for hash chain exhaustion are avoided, reducing complexity and improving robustness. BRIEF DESCRIPTION OF THE DRAWINGS

[0052] Figure 1 The present invention provides a flow chart of a physical layer authentication mechanism applicable to the Internet of Things and a watermark update method based on a one-way hash chain.

[0053] Figure 2 Schematic diagram of an Internet of Things communication model containing four types of communication entities provided by an embodiment of the present invention.

[0054] Figure 3 This is a schematic diagram of the physical layer frame structure and preamble watermark replacement solution provided by an embodiment of the present invention.

[0055] Figure 4 It is the authentication pass rate of valid frames, invalid frames, and replayed frames under two strategies: using only hash value verification and using a dual authentication process that combines correlation value judgment and hash value verification. DETAILED DESCRIPTION

[0056] The accompanying drawings are for illustrative purposes only and are not to be construed as limiting this patent;

[0057] In order to better illustrate this embodiment, some parts in the drawings may be omitted, enlarged, or reduced, and do not represent the actual product size;

[0058] It is understandable to those skilled in the art that some well-known structures and their descriptions may be omitted in the drawings.

[0059] This embodiment is aimed at the application scenario of low-power wide-area Internet of Things, and realizes a safe, reliable and low-computational complexity authentication method by introducing spread spectrum code watermarks. In view of the strategy design of the sender to replace the watermark position of the signal, a solution is proposed to generate a position index using authentication tags and the Knuth-Durstenfeld shuffling algorithm. Subsequently, in response to the problem of watermark replacement selection and the need to resist replay attacks, the watermark sequence is updated by introducing a one-way hash chain. In response to the verification requirements of the receiver, a low-complexity hypothesis testing method that does not rely on channel estimation is designed, and it is combined with the hash verification method to form a complete message authentication process. At the same time, in response to the problem of limited length of the one-way hash chain, the problem of tail node distribution after the hash chain initialization is solved by utilizing the authentication function of the old hash chain node, thereby realizing hash chain regeneration without restarting the upper-layer protocol authentication process.

[0060] The technical solution of the present invention is further described below with reference to the accompanying drawings and embodiments.

[0061] Example 1

[0062] This embodiment provides a physical layer authentication mechanism applicable to the Internet of Things and a watermark update method based on a one-way hash chain. Figure 1 As shown, the following steps are included:

[0063] S1: Before starting message transmission, the legitimate sender generates a random number and generates a hash chain by processing the random number;

[0064] S2: The legitimate sender and the legitimate receiver establish a shared symmetric key through upper-layer protocol authentication, and the legitimate sender sends the tail node of the hash chain to the legitimate receiver;

[0065] S3: During the message transmission phase, the legitimate sender generates an authentication tag based on the shared symmetric key and the message code element of the payload portion of the physical frame in each frame transmission period, and generates a first replacement position index set based on the authentication tag;

[0066] S4: The legitimate sender selects the corresponding node on the hash chain and replaces the chip at the position corresponding to the chip replacement position index set in the preamble chip sequence in the physical frame with the watermark sequence corresponding to the node. When the hash chain node of the legitimate sender is exhausted, the legitimate sender regenerates a new hash chain and puts the tail node of the new hash chain in the message frame generated by the watermark sequence using the head node of the old hash chain and sends it to the legitimate receiver;

[0067] S5: After the legal receiver detects the physical frame, it generates a label based on the shared symmetric key and the demodulated message codewords and obtains a second replacement index set;

[0068] S6: The legitimate receiver locates the received signal at the chip replacement position corresponding to the physical frame using the second replacement index set, and searches for the watermark sequence with the highest correlation value with the received signal in the watermark sequence set using a correlation energy detection method. The watermark sequence set is preset on the legitimate receiver.

[0069] S7: The legitimate receiver uses the watermark sequence with the highest correlation value with the received signal and the corresponding preamble reference signal at the position of the corresponding code chip replacement in the physical frame to perform matched filtering on the received signal and obtain a statistical check value. If the statistical check value is less than 0, the legitimate receiver determines that the received signal is illegal and discards it. If the statistical check value is greater than 0, the process proceeds to step S8;

[0070] S8: The legal receiver uses the watermark sequence with the highest correlation value with the received signal to restore the corresponding hash node, and obtains the calculation result after several operations. The calculation result is then compared with the last hash node that passed the verification. If the two are equal, the legal receiver determines that the received signal is legal and the hash node passes the verification; if the two are not equal, the receiver determines that the received signal is illegal and discards it.

[0071] For specific application scenario models, please refer to Figure 2 The network contains four types of communication entities: IoT terminals as legitimate senders, base stations as legitimate receivers, IoT terminals that are not authorized to register with the network, and malicious terminals with high computing power that attempt to disrupt network operations by sending forged or replayed signals to base stations. Low-cost legitimate terminal devices lack channel estimation or have only limited channel estimation accuracy. Unregistered terminals have not yet implemented physical layer authentication schemes, and the signals they send to base stations do not contain any physical layer authentication tags. When receiving signals from such terminals, base stations should treat them as invalid and reject them. Malicious terminals will eavesdrop on communications between legitimate senders and receivers, attempting to save historical data sent by legitimate terminals or forge fake frames based on the information obtained through eavesdropping.

[0072] In this IoT communication network, both the sender and receiver utilize single-carrier communication. The generated physical frames undergo direct sequence spread spectrum (DSSS) and are then transmitted using 2FSK modulation. The receiver uses the physical frame's preamble sequence for frame detection and synchronization. The network operates in a frame cycle mode, with frame cycle indices denoted as i∈1,2,3,…. During each frame cycle, the base station is expected to receive at most one physical frame.

[0073] Example 2

[0074] This embodiment, based on the first embodiment, further discloses the following contents:

[0075] In the key establishment phase before sending a message, the legitimate sender needs to generate a one-way hash chain to indicate the selection strategy for replacing the watermark sequence s in the subsequent message sending phase. In this phase, the one-way hash chain is generated as shown in step S1. In step S1, the random number x is continuously concatenated, hashed, and truncated K+1 times to generate a hash chain H with a length of K+1. K →H K-1 →…→H0, specifically:

[0076] S1.1: The sender generates a random number x as a starting seed and selects a hash function h(·) that can output an M-bit binary sequence;

[0077] S1.2: In practical applications, it is possible to replace the set of watermark sequences It is often a pseudo-random code that conforms to the orthogonal property. The size of the set W is usually smaller than the possible value of h(x), that is, W<2 M Therefore, in order to To establish a one-to-one correspondence between the hash nodes, h(x) needs to be truncated to obtain the head node H of the hash chain K :

[0078]

[0079] Where, From position u K Start by intercepting log2W bits of the sequence h(x) and use i K Indicates that node H is expected to be used K The frame period index is u K =i K mod(M-log2 W), W is the size of the watermark sequence set;

[0080] S1.3: Next, we need to generate the remaining K nodes in the hash chain in sequence, according to the generated nodes H j , computing node H j-1 :

[0081]

[0082] Where H j ‖i j Indicates that node H j and the expected use of node H j Frame period index i j The spliced ​​together

[0083] Sequence, u j =i j-1mod(M-log2W), j=1, 2, ..., K; because the truncation operation will offset some of the original anti-collision properties of the hash operation, the embodiment of the present invention uses a sequence splicing operation and changes the starting position of the truncation operation to increase the uncertainty of the hash chain generation result, making it more difficult for malicious terminals to predict;

[0084] S1.4: After repeating step S1.3 K times, the legitimate sender finally generates a one-way hash chain H with a length of K+1. K →H K-1 →…→H0.

[0085] Since the hash function is one-way, that is, if x is known, y = h(x) can be easily calculated, but to calculate x = h in reverse -1 (y) is almost impossible, and the use of a one-way hash chain can protect the authentication tag and watermark sequence from being eavesdropped and replayed.

[0086] In step S2, the legitimate sender and the legitimate receiver establish a shared symmetric key k through upper layer protocol authentication, and the legitimate sender sends the tail node H0 of the hash chain to the legitimate receiver.

[0087] In step S3, the legitimate sender generates an authentication tag t according to the shared key k and the message code element of the physical frame payload in the i-th frame transmission cycle. i , and according to the certification label t i Generate the first replacement position index set Specifically:

[0088] The legitimate sender generates the message code element m in the physical frame payload part during the i-th frame transmission cycle. i , using a secure and robust hash function g(·,·) to generate the authentication tag t i :

[0089] t i =g(m i ,k)

[0090] Generate an initial replacement position indication sequence z0 = [1, 1, 1, ..., 0, 0, ..., 0], the length of the initial replacement position indication sequence z0 is L, the values ​​of the first N elements are all 1, and the values ​​of the remaining elements are 0, and t i After setting it as the seed of the pseudo-random number generator, the Knuth-Durstenfeld shuffling algorithm is used to shuffle the cards to obtain the corresponding z i :

[0091] PRNG(t i )

[0092] z i=shuffle(z0)

[0093] Where, PRNG(t i ) means setting the random number seed, shuffle(z0) means calling the shuffle algorithm to shuffle the order, sequence z i The set of element subscripts with a median value of 1 is the first replacement position index set

[0094] Step S4 specifically includes:

[0095] When the legitimate sender selects the corresponding node on the hash chain, the hash chain is used in reverse, specifically:

[0096] Let the period index of the legitimate sender sending the message to be authenticated for the first time be t. At this time, the legitimate sender should use the watermark sequence corresponding to node H1 to replace the preamble code chip. At the next period t+1, the sender uses the watermark sequence corresponding to H2 to replace the preamble code chip. Similarly, at period t+k, the sender should use H k+1 The corresponding watermark sequence replaces the preamble code chips;

[0097] In step S4, the chip at the position corresponding to the chip replacement position index set in the preamble chip sequence in the physical frame is replaced with the watermark sequence corresponding to the node, specifically:

[0098] Different from the existing spread spectrum code authentication technology in GNSS that replaces the spread spectrum code, the present invention directly replaces the chip sequence of the preamble code of the physical frame after the spread spectrum. Let the original preamble code sequence without watermark be expressed as p = [p1, p2, ..., p L ],p k ∈{-1,1}, the sender needs to replace part of the code chips in p with the watermark sequence s=[s1,s2,…,s N ],s k ∈{-1,1}, the replacement rule can be expressed as follows:

[0099]

[0100] Where, like Figure 3 shown.

[0101] According to the replacement principle, the legitimate sender needs to watermark the preamble code sequence after spread spectrum in two stages. The first stage is to generate the first replacement position index set. The second is to select the watermark sequence s for replacement. In the embodiment of the present invention, the first replacement position index set The authentication tag generated by the legitimate sender based on the shared key k and the physical frame payload is obtained through mapping, and the value of s is determined by the one-way hash chain pre-generated by the legitimate sender in the key establishment phase.

[0102] Because the length of a one-way hash chain is limited, it faces the problem of node exhaustion during use. When all nodes in the hash chain are exhausted, the sender needs to regenerate a new hash chain and distribute the tail node of the new chain to the receiver. If the signature authentication technology of the upper layer of the protocol stack is reactivated every time a new tail node is issued, it will seriously undermine the efficiency of the system and obscure the original advantages of the physical layer authentication scheme. To avoid the use of computationally intensive upper-layer authentication protocols during hash chain regeneration, embodiments of the present invention adopt a simple hash chain regeneration mechanism that can achieve efficient distribution of tail nodes during hash chain reinitialization.

[0103] In step S4, when the hash chain nodes of the legitimate sender are exhausted, the legitimate sender regenerates a new hash chain and puts the tail node of the new hash chain in the message frame generated by the head node of the old hash chain to generate the watermark sequence and sends it to the legitimate receiver, using i K Indicates the use of H K The frame period index is:

[0104] S4.1: The legitimate sender regenerates a new seed value x′ and generates a new hash chain of length K+1: H′ according to steps S1.2 to S1.4. K →H′ K-1 →…→H′0;

[0105] S4.2: In the i K In a cycle, the legitimate sender puts the new tail node H′0 in the message to be sent in this cycle, and uses H K The corresponding watermark sequence watermarks the signal;

[0106] S4.3: The legal recipient is in the i K The corresponding signal is received in a cycle, and the legitimacy of the signal is verified to obtain the tail node H′0 of the new hash chain;

[0107] S4.4: The old hash chain is exhausted, and then the new hash chain H′ is generated. K →H′ K-1 →…→H′0 is put into use, and when the new hash chain is about to be exhausted, the legitimate sender and the legitimate receiver continue to generate a new hash chain for use in the manner of steps S4.1 to S4.3.

[0108] During the message reception phase, the legitimate receiver needs to verify the legitimacy of the message after detecting it from the terminal. For the physical frame received in period i, the receiver's authentication process is as follows:

[0109] In step S5, after the legal receiver detects the physical frame, it despreads and demodulates the payload portion to obtain And use the hash function g(·,·) to generate the authentication tag Generate an initial replacement position indicator sequence The initial replacement position indication sequence The length is L, the first N elements have the value 1, and the rest have the value 0. After setting it as the seed of the pseudo-random number generator, the Knuth-Durstenfeld shuffling algorithm is used to shuffle the cards to obtain the corresponding sequence The set of element subscripts with a median value of 1 is the second replacement position index set I′.

[0110] In step S6, the legitimate receiver locates the received signal r at the corresponding chip replacement position of the physical frame through the second replacement index set I′ i , and detect the watermark sequence using the correlation energy detection method Search out and receive signal r i The watermark sequence with the highest correlation value

[0111]

[0112] In step S7, the legitimate receiver uses the watermark sequence with the highest correlation value with the received signal The preamble reference signal p at the second replacement position index set I′ corresponding to the physical frame I′ and the received signal r i Perform matched filtering and obtain the statistical test value τ i :

[0113]

[0114] If τ i <0, the legal receiver determines the received signal as illegal and discards it. i >0, then go to step S8.

[0115] In step S8, the legitimate receiver uses the watermark sequence with the highest correlation value with the received signal Restore the corresponding hash node Let the last verified hash node value be recorded as And order Represents a hash node Perform k consecutive splicing, hashing, and truncating operations to generate hash nodes. After ij splicing, hashing, and truncating operations, we get Compare If the value of The legal receiver determines that the received signal is legal if The legal receiver then determines that the received signal is illegally discarded.

[0116] Example 3

[0117] This embodiment uses the methods of Embodiment 1 and Embodiment 2 to compare the authentication pass rates of valid frames, invalid frames, and replayed frames under different signal-to-noise ratio environments when using only the hash chain check authentication method and the authentication method combining correlation value judgment and hash chain check proposed by the present invention.

[0118] like Figure 4 As shown, Figure 4 Described in 10 5 A comparison of the authentication pass rates for valid, invalid, and replayed frames under different signal-to-noise ratio environments is presented for different one-way hash chain usage periods of 17 bars, when the system uses only hash chain verification and when it uses the authentication method proposed in this invention, which combines correlation value determination with hash chain verification. This shows that the dual authentication process using the method of this embodiment can provide the system with a certain degree of resistance to replay attacks while minimizing the risk of invalid frames.

[0119] The same or similar reference numerals correspond to the same or similar components;

[0120] The terms used in the drawings to describe positional relationships are for illustrative purposes only and should not be construed as limiting this patent;

[0121] Obviously, the above embodiments of the present invention are merely examples for the purpose of clearly illustrating the present invention, and are not intended to limit the embodiments of the present invention. Those skilled in the art will appreciate that other variations or modifications can be made based on the above description. It is not necessary and impossible to enumerate all embodiments here. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention shall be included within the scope of protection of the claims of the present invention.

Claims

1. A physical layer authentication mechanism applicable to the Internet of Things and a watermark update method based on a one-way hash chain, characterized in that: The following steps are involved: S1: Before starting message transmission, the legitimate sender generates a random number and generates a hash chain by processing the random number; S2: The legitimate sender and the legitimate receiver establish a shared symmetric key through upper-layer protocol authentication, and the legitimate sender sends the tail node of the hash chain to the legitimate receiver; S3: During the message transmission phase, the legitimate sender generates an authentication tag based on the shared symmetric key and the message code element of the payload portion of the physical frame in each frame transmission period, and generates a first replacement position index set based on the authentication tag; S4: The legitimate sender selects the corresponding node on the hash chain and replaces the chip at the position corresponding to the chip replacement position index set in the preamble chip sequence in the physical frame with the watermark sequence corresponding to the node. When the hash chain node of the legitimate sender is exhausted, the legitimate sender regenerates a new hash chain and puts the tail node of the new hash chain in the message frame generated by the watermark sequence using the head node of the old hash chain and sends it to the legitimate receiver; S5: After the legal receiver detects the physical frame, it generates a label based on the shared symmetric key and the demodulated message codewords and obtains a second replacement index set; S6: The legitimate receiver locates the received signal at the chip replacement position corresponding to the physical frame using the second replacement index set, and searches for the watermark sequence with the highest correlation value with the received signal in the watermark sequence set using a correlation energy detection method. The watermark sequence set is preset on the legitimate receiver. S7: The legitimate receiver uses the watermark sequence with the highest correlation value with the received signal and the corresponding preamble reference signal at the position of the corresponding code chip replacement in the physical frame to perform matched filtering on the received signal and obtain a statistical check value. If the statistical check value is less than 0, the legitimate receiver determines that the received signal is illegal and discards it. If the statistical check value is greater than 0, the process proceeds to step S8; S8: The legal receiver uses the watermark sequence with the highest correlation value with the received signal to restore the corresponding hash node, and obtains the calculation result after several operations. The calculation result is then compared with the last hash node that passed the verification. If the two are equal, the legal receiver determines that the received signal is legal and the hash node passes the verification; if the two are not equal, the receiver determines that the received signal is illegal and discards it.

2. The physical layer authentication mechanism applicable to the Internet of Things and the watermark update method based on a one-way hash chain according to claim 1 are characterized in that: In step S1, the random number x is concatenated, hashed, and truncated K+1 times continuously to generate a hash chain H with a length of K+1. K →H K-1 →…→H0, specifically: S1.1: The sender generates a random number x as a starting seed and selects a hash function h(·) that can output an M-bit binary sequence; S1.2: Use the hash function h(·) and the random number x to generate the sequence h(x), and truncate h(x) to get the head node H of the hash chain. K : Where, From position u K Start by intercepting log2W bits of the sequence h(x) and use i K Indicates that node H is expected to be used K The frame period index is u K =i K mod(M-log2W), W is the size of the watermark sequence set; S1.3: Based on the generated node H j , computing node H j-1 : Where H j ||i j Indicates that node H j and the expected use of node H j Frame period index i j The sequence obtained by splicing, u j =i j-1 mod(M-log2W), j=1, 2,...,K; S1.4: After repeating step S1.3 K times, the legitimate sender finally generates a one-way hash chain H with a length of K+1. K →H K-1 →…→H0.

3. The physical layer authentication mechanism applicable to the Internet of Things and the watermark update method based on a one-way hash chain according to claim 2 are characterized in that: In step S2, the legitimate sender and the legitimate receiver establish a shared symmetric key k through upper layer protocol authentication, and the legitimate sender sends the tail node H0 of the hash chain to the legitimate receiver.

4. The physical layer authentication mechanism applicable to the Internet of Things and the watermark update method based on a one-way hash chain according to claim 3 is characterized in that: In step S3, the legitimate sender generates an authentication tag t according to the shared key k and the message code element of the physical frame payload in the i-th frame transmission cycle. i , and according to the certification label t i Generate the first replacement position index set Specifically: The legitimate sender generates the message code element m in the physical frame payload part during the i-th frame transmission cycle. i , using hash function g(·,·) to generate authentication tag t i : t i =g(m i ,k) Generate an initial replacement position indication sequence z0 = [1, 1, 1, ..., 0, 0, ..., 0], the length of the initial replacement position indication sequence z0 is L, the values ​​of the first N elements are all 1, and the values ​​of the remaining elements are 0, and t i After setting it as the seed of the pseudo-random number generator, the Knuth-Durstenfeld shuffling algorithm is used to shuffle the cards to obtain the corresponding z i , sequence z i The set of element subscripts with a median value of 1 is the first replacement position index set 5. The physical layer authentication mechanism applicable to the Internet of Things and the watermark update method based on a one-way hash chain according to claim 4 is characterized in that: Step S4 specifically includes: When the legitimate sender selects the corresponding node on the hash chain, the hash chain is used in reverse, specifically: Let the period index of the legitimate sender sending the message to be authenticated for the first time be t. At this time, the legitimate sender should use the watermark sequence corresponding to node H1 to replace the preamble code chip. At the next period t+1, the sender uses the watermark sequence corresponding to H2 to replace the preamble code chip. Similarly, at period t+k, the sender should use H k+1 The corresponding watermark sequence replaces the preamble code chips; In step S4, the chip at the position corresponding to the chip replacement position index set in the preamble chip sequence in the physical frame is replaced with the watermark sequence corresponding to the node, specifically: Let the original unwatermarked preamble code sequence be expressed as p = [p1, p2, ..., p L ], p k ∈{-1, 1}, the sender needs to replace part of the code chips in p with the watermark sequence s=[s1, s2, ..., s N ],s k ∈{-1, 1}, the replacement rule can be expressed as follows: Where, 6. The physical layer authentication mechanism applicable to the Internet of Things and the watermark update method based on a one-way hash chain according to claim 5, characterized in that: In step S4, when the hash chain nodes of the legitimate sender are exhausted, the legitimate sender regenerates a new hash chain and puts the tail node of the new hash chain in the message frame that generates the watermark sequence using the head node of the old hash chain and sends it to the legitimate receiver. Specifically: S4.1: The legitimate sender regenerates a new seed value x′ and generates a new hash chain of length K+1: H′ according to steps S1.2 to S1.

4. K →H′ K-1 →…→H′0; S4.2: In the i K In a cycle, the legitimate sender puts the new tail node H′0 in the message to be sent in this cycle, and uses H K The corresponding watermark sequence watermarks the signal; S4.3: The legal recipient is in the i K The corresponding signal is received in a cycle, and the legitimacy of the signal is verified to obtain the tail node H′0 of the new hash chain; S4.4: The old hash chain is exhausted, and then the new hash chain H′ is generated. K →H′ K-1 →…→H′0 is put into use, and when the new hash chain is about to be exhausted, the legitimate sender and the legitimate receiver continue to generate a new hash chain for use in the manner of steps S4.1 to S4.

3.

7. The physical layer authentication mechanism and watermark update method based on a one-way hash chain applicable to the Internet of Things according to claim 6 is characterized in that: In step S5, after the legal receiver detects the physical frame, it despreads and demodulates the payload portion to obtain And use the hash function g(·,·) to generate the authentication tag Generate an initial replacement position indicator sequence The initial replacement position indication sequence The length is L, the first N elements have the value 1, and the rest have the value 0. After setting it as the seed of the pseudo-random number generator, the Knuth-Durstenfeld shuffling algorithm is used to shuffle the cards to obtain the corresponding sequence The set of element subscripts with a median value of 1 is the second replacement position index set I′.

8. The physical layer authentication mechanism applicable to the Internet of Things and the watermark update method based on a one-way hash chain according to claim 7 is characterized in that: In step S6, the legitimate receiver locates the received signal r at the corresponding chip replacement position of the physical frame through the second replacement index set I′ i , and detect the watermark sequence using the correlation energy detection method Search out and receive signal r i The watermark sequence with the highest correlation value 9. The physical layer authentication mechanism applicable to the Internet of Things and the watermark update method based on a one-way hash chain according to claim 8, characterized in that: In step S7, the legitimate receiver uses the watermark sequence with the highest correlation value with the received signal The preamble reference signal p at the second replacement position index set I′ corresponding to the physical frame I′ and the received signal r i Perform matched filtering and obtain the statistical test value τ i : If τ i <0, the legal receiver determines the received signal as illegal and discards it. i >0, then go to step S8.

10. The physical layer authentication mechanism applicable to the Internet of Things and the watermark update method based on a one-way hash chain according to claim 9, characterized in that: In step S8, the legitimate receiver uses the watermark sequence with the highest correlation value with the received signal Restore the corresponding hash node Let the last verified hash node value be recorded as And order Represents a hash node Perform k consecutive splicing, hashing, and truncating operations to generate hash nodes. After ij splicing, hashing, and truncating operations, we get Compare and If the value of The legal receiver determines that the received signal is legal if The legal receiver then determines that the received signal is illegally discarded.

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