Key extraction method based on bucket replacement and related device

Abstract

The invention discloses a key extraction method based on bucket replacement and a related device, and belongs to the technical field of networking, and the method comprises the steps: constructing a feature sequence of a transmitting end and a feature sequence of a receiving end; constructing n buckets of the sending end based on the feature sequence of the sending end; constructing n buckets of the receiving end based on the feature sequence of the receiving end; performing bit division and sorting on elements in the n buckets of the sending end to obtain a coding bit, an ordered sequence and an index sequence of each bucket of the sending end; generating a secret key and a region replacement table of the sending end according to the coding bit, the ordered sequence and the index sequence of each bucket of the sending end; the secret key of the receiving end is generated based on the area permutation table and the n buckets of the receiving end, the method and the related device can achieve secret key extraction, and the method and the related device have the advantages of being high in safety, high in real-time performance and low in resource occupation.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of networking, and relates to a key extraction method based on bucket replacement and related devices. BACKGROUND

[0002] With the continuous development of artificial intelligence, the application of robot cluster technology in industrial inspection, low-altitude logistics, emergency rescue and other scenarios is becoming more and more widespread. In order to realize the cooperative perception and decision-making among multiple robots, these systems usually adopt a distributed wireless communication architecture, so that each node can complete information sharing and path coordination under the condition of no central control. In this context, once the wireless link encounters threats such as interference, forgery or tampering, it may cause task deviation, command deviation, and even cause personal injury in severe cases. Therefore, the security design for robot cluster communication is crucial.

[0003] Existing security protection mainly relies on upper-layer cryptography mechanisms, but as the cluster size continues to expand, the existing mechanisms have increasingly prominent problems such as the overhead of key distribution and management. At the same time, with the continuous development of high-performance computing technology, cryptography mechanisms based on computational complexity are facing the potential threat of being cracked. Physical layer key extraction technology generates shared keys by utilizing the randomness and reciprocity of legitimate links, naturally suppresses eavesdropping through spatial decorrelation, and has the characteristics of fast key generation. This technology can complement the upper-layer cryptography and jointly build a multi-dimensional and three-dimensional security protection system from the physical layer to the protocol layer.

[0004] However, the existing physical layer key extraction scheme has obvious deficiencies in the robot cluster communication scenario. In typical schemes, the channel feature sequence is quantized, making it difficult to avoid loss of effective information. In order to obtain consistent keys, the communication parties need to carry out multiple rounds of open negotiation, which introduces a large system overhead, not only reducing the key generation rate, but also possibly causing leakage risk in the negotiation process. To improve the consistency of the initial key, existing technologies introduce channel coding and globally adjust the entire channel feature sequence to construct a code word structure, but this brings problems including: (1) The algorithm complexity and processing delay increase significantly with the growth of sequence length, making it difficult to meet real-time requirements; (2) The bit consumption in the information interaction stage consumes a large number of bit resources, with high system resource occupation and low efficiency. SUMMARY

[0005] The purpose of the present application is to overcome the shortcomings of the prior art and provide a key extraction method based on bucket replacement and related devices, which can extract keys and have the characteristics of high security, strong real-time performance and low resource occupation.

[0006] To achieve the above objectives, this invention discloses a key extraction method based on bucket permutation, comprising: Constructing the feature sequence of the sending end and the characteristic sequence of the receiving end ; Based on the feature sequence of the sending end Construct n buckets for the sender Based on the feature sequence of the receiving end Construct n buckets at the receiving end ; For the n buckets of the sending end The elements in the data are divided into bits and sorted to obtain the encoded bits of each bucket at the sending end. ordered sequence and index sequence ; According to the encoded bits of each bucket at the sending end ordered sequence and index sequence Generate the key and region permutation table for the sending end; Based on the aforementioned region permutation table and the n buckets at the receiving end. Generate the key for the receiving end.

[0007] Furthermore, the construction of the feature sequence of the sending end The process is as follows: The transmitting and receiving ends transmit pilot sequences sequentially within the same time frame. The transmitting end performs channel estimation based on the received pilot signals to obtain the channel estimation result. Feature extraction is then performed on the channel estimation result, and a feature sequence for the transmitting end is constructed based on the extracted features. .

[0008] Furthermore, the feature sequence based on the sending end Construct n buckets for the sender The process is as follows: The transmitting end uses the feature sequence of the transmitting end according to the preset bucket width m. Divide the data into intervals to obtain n buckets at the sending end. .

[0009] Furthermore, the n buckets at the sending end The elements in the data are divided into bits and sorted to obtain the encoded bits of each bucket at the sending end. ordered sequence and index sequence The process is as follows: For the n buckets of the sending end Perform bit partitioning separately to obtain the encoded bits of each bucket at the sending end. and permutation The permutation position of each bucket at the sending end. The elements in the data are sorted in ascending order to obtain an ordered sequence of buckets at the sending end. and index sequence .

[0010] Furthermore, the step of using the encoded bits of each bucket at the sending end... ordered sequence and index sequence The process of generating the sender's key and region permutation table is as follows: The encoded bits of each bucket at the transmitting end Quantization is performed to obtain the quantization results of each bucket at the sending end. And based on the quantization results of each bucket at the sending end. Construct the quantized sequences of each bucket at the sending end; The quantized sequences of each bucket at the transmitting end are encoded to obtain the encoded sequence and parity bit of each bucket at the transmitting end. ; The encoded sequences of each bucket at the sending end are combined to obtain the key of the sending end; The check bits of each bucket at the sending end Combine them to obtain the combined check bits. The ordered sequence of each bucket at the sending end By combining, we obtain a combined ordered sequence. According to the combined check bits Combined ordered sequences and index sequence Generate a region permutation table.

[0011] Furthermore, the process of encoding the quantized sequence of each bucket at the sending end is as follows: The quantized sequences of each bucket at the transmitting end are encoded using a block coding method.

[0012] Furthermore, the n buckets based on the region permutation table and the receiving end... The process of generating the receiver's key is as follows: For the n buckets of the receiving end Perform bit partitioning to obtain the encoded bits of each bucket at the receiving end. and permutation ; According to the region permutation table Replacement of each bucket at the receiving end Rearrange the buckets to obtain the permutation sequence for each bucket at the receiving end. ; The permutation sequence of each bucket at the receiving end The encoded bits of each bucket at the receiving end The codeword sequences of each bucket at the receiving end are combined to obtain the codeword sequences of each bucket at the receiving end. Decoding is then performed on the codeword sequences of each bucket at the receiving end to obtain the decoding results of each bucket at the receiving end. The decoding results of each bucket at the receiving end Combine the keys to obtain the receiving key.

[0013] This invention discloses a key extraction system based on bucket permutation, comprising: The first construction module is used to construct the feature sequence of the sending end. and the characteristic sequence of the receiving end ; The second construction module is used to construct based on the feature sequence of the sending end. Construct n buckets for the sender Based on the feature sequence of the receiving end Construct n buckets at the receiving end ; The sorting module is used to sort the n buckets of the sending end. The elements in the data are divided into bits and sorted to obtain the encoded bits of each bucket at the sending end. ordered sequence and index sequence ; The first generation module is used to generate data based on the encoded bits of each bucket at the sending end. ordered sequence and index sequence Generate the key and region permutation table for the sending end; The second generation module is used to generate data based on the region permutation table and the n buckets at the receiving end. Generate the key for the receiving end.

[0014] The present invention discloses a computer device, including a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the processor executes the computer program to implement the steps of the key extraction method based on bucket permutation.

[0015] The present invention discloses a computer-readable storage medium storing a computer program, which, when executed by a processor, implements the steps of the key extraction method based on bucketing permutation.

[0016] The present invention has the following beneficial effects: In practical operation, the key extraction method and related apparatus based on bucket permutation described in this invention, according to the encoded bits of each bucket at the sending end... ordered sequence and index sequence The system generates a key and region permutation table for the sending end, employing a bucket permutation technique. This significantly reduces bit overhead during information exchange, resulting in lower system resource consumption and better real-time performance. Furthermore, based on the region permutation table and the n buckets at the receiving end... The key for the receiver is generated. During the entire generation process, the receiver and transmitter can extract the key through only one one-way information exchange, avoiding repeated information exchanges and improving the security of the system. Attached Figure Description

[0017] To more clearly illustrate the technical solutions of the embodiments of this application, the drawings used in the description of the embodiments of this application will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0018] Figure 1 This is a flowchart of the method of the present invention; Figure 2 This is a schematic diagram of bit partitioning and region permutation table generation in this invention; Figure 3 This is a graph showing the variation of bit overhead with key length in this invention; Figure 4 This is a graph showing the variation of the key inconsistency rate under different code rates according to the present invention. Detailed Implementation

[0019] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0020] The accompanying drawings illustrate various structural schematic diagrams according to embodiments disclosed in this invention. These drawings are not to scale, and some details have been enlarged for clarity, and some details may have been omitted. The shapes of the various regions and layers shown in the drawings, as well as their relative sizes and positional relationships, are merely exemplary and may deviate from reality due to manufacturing tolerances or technical limitations. Furthermore, those skilled in the art can design regions / layers with different shapes, sizes, and relative positions as needed.

[0021] Example 1 refer to Figure 1 and Figure 2The key extraction method based on bucket permutation described in this invention includes the following steps: 1) Construct the feature sequence of the sending end and the characteristic sequence of the receiving end ; The transmitting and receiving ends transmit pilot sequences sequentially within the same time frame. Based on the received pilot signals, the transmitting and receiving ends obtain channel estimation results using least squares or least mean square error. Feature extraction is then performed on the channel estimation results, and a feature sequence for the transmitting end is constructed based on the extracted features. and the characteristic sequence of the receiving end Among them, the characteristic sequence of the sending end and the characteristic sequence of the receiving end The length of each feature is L, and the extracted features include amplitude, phase, and joint features.

[0022] 2) Based on the feature sequence of the sending end Construct n buckets for the sender Based on the feature sequence of the receiving end Construct n buckets at the receiving end ; The transmitting end uses the feature sequence of the transmitting end according to the preset bucket width m. Divide the data into intervals to obtain n buckets at the sending end. Specifically, the feature sequence of the sending end is processed from left to right. m adjacent elements are grouped into the same bucket, forming Given n buckets, obtain the n buckets from the sending end. When there are fewer than m elements at the end, they are padded according to a predetermined alignment rule, which may be zero-padding.

[0023] The receiver uses the characteristic sequence of the receiver according to the bucket width m. Divide the interval into n buckets at the receiving end. The preset bucket width and code length are the same.

[0024] 3) For the n buckets of the sending end The bits are partitioned and sorted separately to obtain the encoded bits of each bucket at the sending end. ordered sequence and index sequence ; like Figure 1 As shown, for the n buckets at the sending end Perform bit partitioning to form the encoded bits for each bucket at the sending end. and permutation ; wherein, the encoded bits Includes bucket The first k elements in the array, permuted Includes bucket The remaining elements excluding the coded bits, the choice of k is related to the code rate R, that is... Then, the permutation bits of each bucket at the sending end are... The elements in the data are sorted in ascending order to obtain an ordered sequence of buckets at the sending end. and index sequence , where the index sequence Index in This indicates that the v-th element is in the permutation position after ascending sort. The position in the middle.

[0025] 4) Based on the encoded bits of each bucket at the sending end. ordered sequence and index sequence Generate a region permutation table; Encoding bits for each bucket at the sending end Quantification is performed to obtain the quantification results. And based on the quantification results Construct the quantized sequence; where binary quantization or multi-bit quantization can be used for quantization, the process of using binary quantization is as follows:

[0026] The quantized sequence is encoded to obtain the encoded sequence of each bucket at the sending end. and check bits The encoding is performed using block codes; The encoded sequences of each bucket at the sending end are combined to obtain the sending end's key. The check bit for each bucket at the sending end Combine them to obtain the combined check bits. Simultaneously, the ordered sequence of each bucket at the sending end. By combining, we obtain a combined ordered sequence. Then, based on the combined check bits Combined ordered sequences Generate a region permutation table. Specifically, iterate through the parity bits, setting i=0, and then incrementing by one each time: when =0, select and combine ordered sequences from front to back. The elements in the index sequence, and in the index sequence Find the index j corresponding to the element in the middle; when =1, then select and combine ordered sequences from back to front. The elements in the index sequence, and in the index sequence Find the index j corresponding to the element in the middle; Assign the index j of the search to the region substitution table. ,Right now The process continues until the traversal is complete, at which point a region permutation table is obtained, which is then sent to the receiving end.

[0027] 5) Generate the receiving key based on the aforementioned region permutation table; For the n buckets at the receiving end Perform bit partitioning to obtain the encoded bits of each bucket at the receiving end. and permutation According to the aforementioned region permutation table Replacement of each bucket at the receiving end Rearrange the buckets to obtain the permutation sequence for each bucket at the receiving end. The permutation sequence of each bucket at the receiving end. The encoded bits of each bucket at the receiving end By combining the sequences, the codeword sequences of each bucket at the receiving end are obtained. The codeword sequence for each bucket of the receiving end. Perform decoding to obtain the decoding results of each bucket at the receiving end. The decoding results of each bucket at the receiving end By combining the two, the receiving key is obtained. The codeword sequence This can be seen as writing in an ideal way. By superimposing noise of a preset intensity, interference can be corrected through decoding. Therefore, when the difference in characteristic sequences between the communicating parties is within a certain range, this invention can compensate for non-ideal factors such as noise, thereby extracting a consistent security key.

[0028] Simulation Experiment To evaluate the bit overhead of this invention, the entire feature sequence is adjusted, using the key extraction scheme as a benchmark. Let the extracted key length be L. The benchmark scheme requires transmitting L position indices during the information exchange phase. When each position is... If each bit is encoded, then the total interactive bit overhead is: bit When L=256, the interaction process occupies 2048 bits of bit overhead, and the bit overhead increases significantly with the increase of L. This invention buckets the feature sequence and adjusts the position of the permutation bits within each bucket; therefore, the information interaction sequence of each bucket must contain… The index of each position, where m is the bucket width and R is the encoding bitrate. If each position uses... Each bucket is encoded in bits, with a bit overhead of 1. , The total interaction bit overhead required for each bucket is: bit When L=256, a block code with a code length of 8 and a code rate of 1 / 2 is selected. The total bit overhead of this invention is 256 bits, which is 87.5% lower than the baseline scheme.

[0029] Figure 3 This is a graph showing the bit overhead of the present invention as a function of key length. Figure 3 As can be seen, compared to the baseline scheme, the bit overhead of this invention is reduced by more than an order of magnitude, significantly reducing system overhead. Meanwhile, as the code rate increases, the bit overhead of this invention gradually decreases. This is because, for the same key length, a higher code rate results in a shorter permutation bit length, and consequently, fewer positions need to be adjusted.

[0030] To evaluate the key extraction performance of this invention, the key inconsistency rate of legitimate users under different code rates was compared. This invention skips the quantization stage by using a transmission area permutation table, preserving the information of the original sequence to the greatest extent possible. To evaluate this characteristic, this experiment uses two baseline schemes for comparison. The first baseline scheme is a hard-information key extraction scheme that performs quantization before information exchange, and the second baseline scheme is an extraction scheme that directly generates the key through quantization. Figure 4 The graph shows the key inconsistency rate variation of this invention under different code rates. At the same code rate, the key inconsistency rate of this invention is significantly lower than that of the two benchmark schemes, and this advantage increases with the increase of the signal-to-noise ratio. Furthermore, the lower the code rate, the stronger the error correction capability and the lower the key inconsistency rate. Even at high code rates, the key inconsistency rate of this invention is still lower than that of the hard information scheme using low code rates. This invention has strong key extraction capability; even if there are some differences in the random sources observed by the communicating parties, this invention can obtain an almost identical key with only one interaction.

[0031] Example 2 The key extraction system based on bucket permutation of the present invention includes: The first construction module is used to construct the feature sequence of the sending end. and the characteristic sequence of the receiving end ; The second construction module is used to construct based on the feature sequence of the sending end. Construct n buckets for the sender Based on the feature sequence of the receiving end Construct n buckets at the receiving end ; The sorting module is used to sort the n buckets of the sending end. The elements in the data are divided into bits and sorted to obtain the encoded bits of each bucket at the sending end. ordered sequence and index sequence ; The first generation module is used to generate data based on the encoded bits of each bucket at the sending end. ordered sequence and index sequence Generate the key and region permutation table for the sending end; The second generation module is used to generate data based on the region permutation table and the n buckets at the receiving end. Generate the key for the receiving end.

[0032] The module division in this embodiment is illustrative and represents only one logical functional division. In actual implementation, other division methods may be used. Furthermore, the functional modules in each embodiment of this application can be integrated into a single processor, exist as separate physical entities, or be integrated into a single module. The integrated modules described above can be implemented in hardware or as software functional modules.

[0033] Example 3 A computer device includes a memory, a processor, and a computer program stored in the memory and executable on the processor. When the processor executes the computer program, it implements the steps of the bucket-based key extraction method, for example, including: constructing a feature sequence at the sending end. and the characteristic sequence of the receiving end Based on the feature sequence of the sending end Construct n buckets for the sender Based on the feature sequence of the receiving end Construct n buckets at the receiving end For the n buckets of the sending end The elements in the data are divided into bits and sorted to obtain the encoded bits of each bucket at the sending end. ordered sequence and index sequence According to the encoded bits of each bucket at the sending end ordered sequence and index sequence Generate the sending end's key and region permutation table; based on the region permutation table and the receiving end's n buckets... A key is generated for the receiving end. The memory may include main memory, such as high-speed random access memory (RAM), or non-volatile memory, such as at least one disk storage device. The processor, network interface, and memory are interconnected via an internal bus, which can be an industry-standard architecture bus, a peripheral component interconnection standard bus, or an extended industry-standard architecture bus. The bus can be categorized as an address bus, data bus, or control bus. The memory stores programs; specifically, the program may include program code, which includes computer operation instructions. The memory may include main memory and non-volatile memory, and provides instructions and data to the processor.

[0034] Example 4 A computer-readable storage medium storing a computer program, which, when executed by a processor, implements the steps of the bucket-based key extraction method, for example including: constructing a feature sequence at the sending end. and the characteristic sequence of the receiving end Based on the feature sequence of the sending end Construct n buckets for the sender Based on the feature sequence of the receiving end Construct n buckets at the receiving end For the n buckets of the sending end The elements in the data are divided into bits and sorted to obtain the encoded bits of each bucket at the sending end. ordered sequence and index sequence According to the encoded bits of each bucket at the sending end ordered sequence and index sequence Generate the sending end's key and region permutation table; based on the region permutation table and the receiving end's n buckets... Generate a key for the receiving end. Specifically, the computer-readable storage medium includes, but is not limited to, volatile memory and / or non-volatile memory. The volatile memory may include random access memory (RAM) and / or cache memory, etc. The non-volatile memory may include read-only memory (ROM), hard disk, flash memory, optical disk, magnetic disk, etc.

[0035] Other embodiments of the invention will readily occur to those skilled in the art upon consideration of the specification and disclosure of the invention. This application is intended to cover any variations, uses, or adaptations of the invention that follow the general principles of the invention and include common knowledge or customary techniques in the art not disclosed herein. The specification and examples are to be considered exemplary only, and the true scope and spirit of the invention are indicated by the following claims.

[0036] It should be understood that the present invention is not limited to the precise structure described above and shown in the accompanying drawings, and various modifications and changes can be made without departing from its scope. The scope of the invention is limited only by the appended claims.

[0037] The above description is merely a preferred embodiment of the present invention and does not constitute any limitation on the present invention. Any simple modifications, alterations, or equivalent structural changes made to the above embodiments based on the technical essence of the present invention shall still fall within the protection scope of the present invention.

Claims

1. A key extraction method based on bucket permutation, characterized in that, include: Constructing the feature sequence of the sending end and the characteristic sequence of the receiving end ; Based on the feature sequence of the sending end Construct n buckets for the sender Based on the feature sequence of the receiving end Construct n buckets at the receiving end ; For the n buckets of the sending end The elements in the data are divided into bits and sorted to obtain the encoded bits of each bucket at the sending end. ordered sequence and index sequence ; Based on the encoded bits of each bucket at the sending end ordered sequence and index sequence Generate the key and region permutation table for the sending end; Based on the aforementioned region permutation table and the n buckets at the receiving end. Generate the key for the receiving end.

2. The key extraction method based on bucket permutation according to claim 1, characterized in that, The feature sequence of the sending end is constructed. The process is as follows: The transmitting and receiving ends transmit pilot sequences sequentially within the same time frame. The transmitting end performs channel estimation based on the received pilot signals to obtain the channel estimation result. Feature extraction is then performed on the channel estimation result, and a feature sequence for the transmitting end is constructed based on the extracted features. .

3. The key extraction method based on bucket permutation according to claim 1, characterized in that, The feature sequence based on the sending end Construct n buckets for the sender The process is as follows: The transmitting end uses the feature sequence of the transmitting end according to the preset bucket width m. Divide the data into intervals to obtain n buckets at the sending end. .

4. The key extraction method based on bucket permutation according to claim 1, characterized in that, The n buckets at the sending end The elements in the data are divided into bits and sorted to obtain the encoded bits of each bucket at the sending end. ordered sequence and index sequence The process is as follows: For the n buckets of the sending end Perform bit partitioning separately to obtain the encoded bits of each bucket at the sending end. and permutation The permutation position of each bucket at the sending end. The elements in the data are sorted in ascending order to obtain an ordered sequence of buckets at the sending end. and index sequence .

5. The key extraction method based on bucket permutation according to claim 1, characterized in that, The encoding bits of each bucket at the sending end ordered sequence and index sequence The process of generating the sender's key and region permutation table is as follows: The encoded bits of each bucket at the transmitting end Quantization is performed to obtain the quantization results of each bucket at the sending end. And based on the quantization results of each bucket at the sending end. Construct the quantized sequences of each bucket at the sending end; The quantized sequences of each bucket at the transmitting end are encoded to obtain the encoded sequence and parity bit of each bucket at the transmitting end. ; The encoded sequences of each bucket at the sending end are combined to obtain the key of the sending end; The check bits of each bucket at the sending end Combine them to obtain the combined check bits. The ordered sequence of each bucket at the sending end By combining, we obtain a combined ordered sequence. According to the combined check bits Combined ordered sequences and index sequence Generate a region permutation table.

6. The key extraction method based on bucket permutation according to claim 5, characterized in that, The process of encoding the quantized sequence of each bucket at the transmitting end is as follows: The quantized sequences of each bucket at the transmitting end are encoded using a block coding method.

7. The key extraction method based on bucket permutation according to claim 1, characterized in that, The n buckets based on the region permutation table and the receiving end The process of generating the receiver's key is as follows: For the n buckets of the receiving end Perform bit partitioning to obtain the encoded bits of each bucket at the receiving end. and permutation ; According to the region permutation table Replacement of each bucket at the receiving end Rearrange the buckets to obtain the permutation sequence for each bucket at the receiving end. ; The permutation sequence of each bucket at the receiving end The encoded bits of each bucket at the receiving end The codeword sequences of each bucket at the receiving end are combined to obtain the codeword sequences of each bucket at the receiving end. Decoding is then performed on the codeword sequences of each bucket at the receiving end to obtain the decoding results of each bucket at the receiving end. The decoding results of each bucket at the receiving end Combine the keys to obtain the receiving key.

8. A key extraction system based on bucket permutation, characterized in that, include: The first construction module is used to construct the feature sequence of the sending end. and the characteristic sequence of the receiving end ; The second construction module is used to construct based on the feature sequence of the sending end. Construct n buckets for the sender Based on the feature sequence of the receiving end Construct n buckets at the receiving end ; The sorting module is used to sort the n buckets of the sending end. The elements in the data are divided into bits and sorted to obtain the encoded bits of each bucket at the sending end. ordered sequence and index sequence ; The first generation module is used to generate data based on the encoded bits of each bucket at the sending end. ordered sequence and index sequence Generate the key and region permutation table for the sending end; The second generation module is used to generate data based on the region permutation table and the n buckets at the receiving end. Generate the key for the receiving end.

9. A computer device comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, characterized in that, When the processor executes the computer program, it implements the steps of the key extraction method based on bucket permutation as described in any one of claims 1-7.

10. A computer-readable storage medium storing a computer program, characterized in that, When the computer program is executed by a processor, it implements the steps of the key extraction method based on bucket permutation as described in any one of claims 1-7.

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