A Dynamic Low-Storage White-Box AES Encryption Method for Vehicle-to-Everything (V2X) Communication

Abstract

This invention provides a dynamic, low-storage white-box AES encryption method for vehicle-to-everything (V2X) communication, belonging to the field of V2X communication security technology. The method is applied to an in-vehicle terminal, acquiring dynamic parameters including time slice number, link mode identifier, and area grid identifier. Based on the protected root key and dynamic parameters, a short-lifetime table is derived to generate a seed, and a session key and table generation parameters are temporarily generated accordingly to construct a low-storage half-T-box white-box AES instance. The instance includes a basic half-T-table, an input combination coding layer, column constant groups, rotation multiplexing relationships, and a final round coding table. During encryption, rounds 1 to 9 use half-T-box lookup and rotation multiplexing for column-level output synthesis, and round 10 outputs the encoded ciphertext through the final round coding table. After instance generation, the session key and temporary round key materials are cleared, and the instance is regenerated when the time slice or communication context changes, thereby reducing storage overhead and the risk of explicit key exposure, making it suitable for lightweight deployment of in-vehicle terminals.

Description

Technical Field

[0001] This invention relates to the field of vehicle network communication security technology, and in particular to a dynamic low-storage white-box AES encryption method for vehicle network communication. Background Technology

[0002] With the development of intelligent connected vehicles and vehicle-to-everything (V2X) technology, data interaction between vehicles, roadside facilities, cloud platforms, and other traffic participants is becoming increasingly frequent. V2V, V2I, and V2N communication have become crucial supports for services such as collision warning, emergency braking, collaborative driving, road perception sharing, and remote services. Since V2X communication messages are typically transmitted via open wireless channels, they inherently face security risks such as eavesdropping, tampering, replay attacks, and reverse engineering of terminal software. Therefore, data encryption and key protection at the vehicle terminal side are of paramount importance. V2X communication messages typically exhibit characteristics such as periodic transmission, low-latency transmission, open channel transmission, and limited terminal deployment resources. Therefore, the encryption methods at the vehicle terminal side must simultaneously meet the requirements of lightweight design, low latency, and key protection.

[0003] Advanced Encryption Standard (AES) boasts mature security, a well-developed engineering ecosystem, and widespread software and hardware implementations, leading to its extensive use in vehicle terminals, vehicle communication units, and embedded security modules. However, in typical software execution environments, traditional AES implementations often require storing or retrieving key materials, and round keys and intermediate states may appear observable during runtime. When attackers obtain terminal programs and runtime data through debugging interfaces, firmware extraction, memory dumping, or reverse engineering, the key materials and encryption logic are at risk of being recovered, copied, or reused.

[0004] White-box cryptography, by coupling the key with the encryption logic, reduces the probability of the key being exposed in plaintext using lookup tables, encoding, and obfuscation, making it suitable for software execution environments that are not entirely trusted. Traditional white-box AES typically integrates byte substitution, column mixing, and round key addition into a large-scale lookup table, but the storage overhead of a complete T-box or multi-location table structure is high, making it unsuitable for deployment in vehicle platforms with limited storage resources.

[0005] To reduce storage overhead, some existing lightweight white-box AES solutions use single-table or semi-T-table structures. However, if they still retain directly analyzable round key materials, auxiliary sharding structures, index reverse lookup structures, or output decoding structures, it is still possible for the round keys or the last round structure to be recovered. Furthermore, if the white-box instance remains unchanged for a long period, attackers can continuously collect, compare, and analyze data offline, and even directly move the instance to reuse its encryption capabilities.

[0006] In the context of connected vehicles, communication messages are frequent, context changes are rapid, and real-time requirements are high. Therefore, a method is needed to achieve AES white-box protection with relatively low storage overhead, enabling white-box instances to be updated with time slices and communication context changes, and preventing session keys and temporary round key materials from being retained for a long time in the normal execution environment during the encryption process.

[0007] Therefore, there is an urgent need to provide a dynamic low-storage white-box AES encryption method for vehicle-to-everything (V2X) communication, which can derive session keys and table generation parameters based on dynamic parameters, construct low-storage semi-T-box white-box AES instances, and reduce the risks of explicit key exposure, simple structure recovery, and cross-time window reuse by inputting combined coding layers, column constant groups, rotation multiplexing relations, and final round coding tables. Summary of the Invention

[0008] The purpose of this invention is to provide a dynamic, low-storage white-box AES encryption method for vehicle-to-everything (V2X) communication, which solves the problems of large lookup table storage overhead, long-term fixed instances, easy analysis of key materials, and difficulty in low-latency deployment of vehicle terminals in existing white-box AES implementations.

[0009] To achieve the above objectives, this invention provides a dynamic low-storage white-box AES encryption method for vehicle-to-everything (V2X) communication, applied to an in-vehicle terminal. The method includes: acquiring dynamic parameters corresponding to the current communication, the dynamic parameters including a time slice number, a link mode identifier, and a region grid identifier; inputting the dynamic parameters into a protected key region, which generates a seed short-lifetime table corresponding to the current time window based on a pre-stored stub key and the dynamic parameters, and generates a temporary derived session key and table generation parameters based on the seed short-lifetime table; constructing a low-storage half-T-box white-box AES instance corresponding to the current time window based on the session key and table generation parameters; after the instance is constructed, clearing the session key, temporary round key material, and temporary data generated during the table generation process; calling the low-storage half-T-box white-box AES instance to perform block encryption on the communication data; and regenerating the corresponding low-storage half-T-box white-box AES instance when the time slice or communication context changes.

[0010] The low-storage half-T box white-box AES instance includes a basic half-T table for rounds 1 to 9, an input combination coding layer, column constant groups, and rotational multiplexing relationships, as well as a final round coding table for round 10. Rounds 1 to 9 use the basic half-T table lookup and rotational multiplexing for column-level output synthesis, while round 10 uses the final round coding table for byte-level output processing to obtain the encoded ciphertext.

[0011] The root key is stored in the hardware security module, trusted execution environment, or other protected key area of ​​the vehicle terminal, and ordinary application processes do not directly read the root key. The dynamic parameters can be input into the protected key area, and the protected key area generates a seed short-lifetime table based on the root key. The key derivation algorithm is preferably a hash-based key derivation algorithm. The dynamic parameters are encoded into fixed-length byte strings in a preset order and then participate in key derivation. The time slice number is obtained by dividing a monotonic clock according to a preset time interval. The link mode identifier is used to distinguish different communication modes, communication objects, or session relationships. The area grid identifier is obtained by mapping the vehicle location, roadside unit coverage area, or preset road area.

[0012] The basic semi-T table is used to store the basic AES byte replacement and column mixing contribution corresponding to a single byte. Each entry corresponds to an 8-bit input index and outputs a 32-bit column contribution value consisting of four bytes. By using this basic semi-T table in conjunction with the rotation multiplexing relation, column-level output synthesis can be completed with fewer entries in rounds 1 to 9, thereby reducing the storage overhead of the white-box AES instance.

[0013] The input combination coding layer sets different reversible codes for different byte positions to convert the current round's input byte into a protected lookup index. Specifically, the input combination coding layer in round 1 integrates plaintext bytes, the influence of the initial round key, and input perturbations, while the input combination coding layers in rounds 2 to 9 are used to convert the previous round's coding state into the current round's lookup index.

[0014] The column constant group is generated round by round and column by column. It is derived from the current round key column, the next round state coding compensation and the blinding perturbation. It is used to fuse the current round key in the column output synthesis stage and convert the current round column output into the coded state that can be processed in the next round.

[0015] The final round encoding table is used for the 10th round of processing. The 10th round does not include column mixing operations, and does not use the basic semi-T table, rotation multiplexing relation, and column constant group; the final round encoding table processes the 16-byte encoded state output from the 9th round, completing the 9th round output encoding decoding, byte replacement, row shift mapping, 10th round key fusion, and output encoding to obtain the 16-byte encoded ciphertext.

[0016] Preferably, within the same time slice, the vehicle terminal reuses the low-storage half-T box white-box AES instance already constructed in the current time window to encrypt multiple communication data; when a change in the time slice or communication context is detected, the session key and table generation parameters are re-derived, and the corresponding low-storage half-T box white-box AES instance is regenerated. Preferably, the storage overhead of the low-storage half-T box white-box AES instance is no more than 20KB.

[0017] By adopting the above technical solution, the present invention has the following beneficial effects: It drives session key derivation and white-box instance updates with dynamic parameters, enabling white-box AES instances to be updated according to changes in time windows or communication contexts, reducing the risk of extraction and reuse caused by long-term static instance residency; it reduces the storage size of lookup tables through basic semi-T tables and rotational multiplexing relationships; it integrates the influence of round keys at different stages into the coded state lookup and column output process by inputting combined coding layers, column constant groups, and the final round coding table, reducing the risk of explicit key materials being directly analyzed; and it further reduces the residue of sensitive information by clearing session keys, temporary round key materials, and temporary data during table generation. Thus, it adapts to the encryption protection needs of vehicle terminals in scenarios with low storage, low latency, and dynamic communication. Attached Figure Description

[0018] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention, and those skilled in the art can obtain other drawings based on these drawings without creative effort.

[0019] Figure 1 This is a flowchart illustrating the dynamic low-storage white-box AES encryption method of the present invention.

[0020] Figure 2 This is a schematic diagram of the session key derivation and low-storage half-T-box white-box AES instance generation process of the present invention;

[0021] Figure 3 This is a schematic diagram of the process of the first to ninth rounds of semi-T-box column-level processing and the final round of encoding processing in the tenth round of the present invention. Detailed Implementation

[0022] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. It should be noted that the following embodiments are for illustrative purposes only and are not intended to limit the scope of protection of the present invention. Based on the disclosure of the present invention, equivalent substitutions, simplifications, modifications, or conventional optimizations made by those skilled in the art without creative effort should all fall within the scope of protection of the present invention.

[0023] like Figure 1As shown, this embodiment provides a dynamic low-storage white-box AES encryption method for vehicle-to-everything (V2X) communication, applicable to TBOX, OBU, or other vehicle-mounted terminals with message sending, receiving, and processing capabilities. The vehicle-mounted terminal obtains the dynamic parameters corresponding to the current communication, derives a key based on the root key in the protected area, constructs a low-storage half-T-box white-box AES instance corresponding to the current time window, and calls this instance to perform block encryption on the communication data. This method can be used to perform white-box AES encryption on data packets to be sent before the vehicle sends safety messages, cooperative perception messages, or cooperative control messages.

[0024] exist Figure 1 In the illustrated process, dynamic parameters include a time slice number, a link mode identifier, and a region grid identifier. The time slice number indicates the time window to which the current white-box instance belongs; the link mode identifier distinguishes different communication modes, communication objects, or session relationships; and the region grid identifier, mapped from the vehicle's location, roadside unit coverage area, or a preset road area, represents the coarse-grained spatial region where the current communication is located. These dynamic parameters are encoded into fixed-length byte strings in a preset order and then used in key derivation. The time slice number adapts to the periodic message sending characteristics, the link mode identifier distinguishes different communication objects or session relationships, and the region grid identifier reflects the coarse-grained road or roadside area where the vehicle is located, thus binding the white-box instance to the current communication context.

[0025] The root key is pre-stored in the hardware security module, trusted execution environment, or other protected key area of ​​the vehicle terminal. The system inputs the dynamic parameter encoding result into the protected key area, which executes a key derivation algorithm based on the pre-stored root key and the dynamic parameter encoding result to generate a short-lifetime table generation seed corresponding to the current time window. The ordinary application side temporarily derives the AES-128 session key and white-box instance generation material based on the short-lifetime table generation seed. Let the root key be... The dynamic parameter encoding result is The key derivation algorithm is The generation of the conversation material can then be represented as:

[0026] in, This represents the session material corresponding to the current time window. The preferred key derivation algorithm is HKDF-SHA256. The session material... Including AES-128 session keys and white-box instance generation materials, it can be represented as:

[0027] in, This represents the AES-128 session key, which is 16 bytes long. This indicates the materials generated by white-box instances; This indicates the byte string concatenation or sequential partitioning relationship. The AES-128 session key is used for temporary round key expansion, and the white-box instance generation material is used to generate the input combination coding layer, column constant group, blinding perturbation, rotation multiplexing related parameters, and final round coding table.

[0028] like Figure 2 As shown, after obtaining the session key and white-box instance generation material, the system performs temporary round key expansion on the session key and constructs a low-storage half-T-box white-box AES instance corresponding to the current time window based on the expansion result and the white-box instance generation material. This instance includes the basic half-T tables for rounds 1 to 9, the input combination coding layer, column constant groups, and rotation multiplexing relationships, as well as the final round coding table for round 10. After the instance is constructed, the system removes the seed, session key, temporary round key material, internal mask, output coding parameters, and other temporary data from the table generation process to reduce the residue of sensitive information in the normal execution environment.

[0029] The underlying semi-T table is used to store the AES byte replacement and column hybrid base contribution corresponding to a single byte. Let the input index be... The AES byte replacement result is The contribution of the basic column can then be expressed as:

[0030] in: : Basic column contribution; AES byte replacement result; GF Finite field multiplication; Pack into 32-bit words according to the preset byte order.

[0031] The input combination encoding layer sets different reversible codes for different byte positions to convert the current round's input byte into a protected lookup table index. Therefore, the input combination encoding can be represented as:

[0032] in: : No. Round Input bytes at byte positions; : Corresponding table index; : An 8×8 invertible binary matrix; : 8-bit bias vector.

[0033] like Figure 3As shown, rounds 1 to 9 employ a semi-T-box lookup table and rotational multiplexing method for column-level output synthesis. For any column in the current round, the system selects the four status bytes corresponding to that column according to the row shift rule, and obtains four protected lookup table indices through the input combination coding layer. After the four protected lookup table indices access the same basic semi-T-table, four 32-bit column contribution values ​​are obtained.

[0034] Suppose that for a certain column in the current round, four 32-bit column contribution values ​​are obtained through a lookup of the basic semi-T table. Then, the 32-bit coded output of that column in the current round can be represented as:

[0035] in: : No. Round The 32-bit encoded state output of the column; This column contains four 32-bit column contribution values ​​corresponding to the four input bytes. : These represent cyclic shifts of 8, 16, and 24 bits respectively; : No. Round The column constants. Thus, the contribution values ​​of the first column are directly XORed, the contribution values ​​of the second column are cyclically shifted by 1 byte before being XORed, the contribution values ​​of the third column are cyclically shifted by 2 bytes before being XORed, and the contribution values ​​of the fourth column are cyclically shifted by 3 bytes before being XORed.

[0036] The column constants are generated round-by-round and column-by-column, and are used to fuse the current round's key during the column output synthesis stage, and to convert the current round's column output into an encoded state that can be processed in the next round. The column constants can then be represented as:

[0037] in: : No. Round Column constants; The current round's key column has an impact; : Next round of state coding compensation; Blinding perturbation.

[0038] Through the combination of the aforementioned basic semi-T-table, input combination coding layer, rotation multiplexing relation, and column constant group, rounds 1 to 9 can complete the column-level output synthesis of the first nine rounds of AES without storing the complete multi-position T-table. Since the column mixing contribution of different byte positions in the same column can be obtained by 32-bit column contribution values ​​through byte-level cyclic shift, the system does not need to store a separate large table for each byte position, thereby reducing the storage overhead of white-box instances.

[0039] After the 9th round, the system reassembles the four columns of 32-bit encoded output into a 16-byte encoded state and proceeds to the 10th round of processing. The 10th round does not include column mixing operations, so it does not use the basic half-T table, rotation multiplexing relation, and column constant group. Instead, it performs byte-level output processing through the final round encoding table.

[0040] The final round encoding table processes the 16-byte encoded state of the 9th round output, used to complete the 9th round output encoding decoding, byte replacement, row shift mapping, 10th round key fusion, and output encoding. Therefore, any output byte of the 10th round can be represented as:

[0041] in: In the 9th round of output coding state, after row shift mapping, it corresponds to the ... Input bytes at each output position; : The encoding at the corresponding position is de-transformed; AES byte replacement; : The key byte corresponding to the 10th round; Output encoding transformation; Round 10 One ciphertext byte output; : The row shift mapping relationship in the 10th round.

[0042] Within the same time slice, the vehicle-mounted terminal can reuse the currently constructed low-storage half-T-box white-box AES instance to perform group encryption on multiple communication data. When the time slice or communication context changes, the system re-acquires dynamic parameters, re-derives the session key and table generation parameters, and reconstructs the corresponding low-storage half-T-box white-box AES instance. In this way, the effective lifespan of a single white-box instance is limited to the current time window or the current communication context, reducing the risk of extraction and reuse caused by long-term static instance residency.

[0043] In this embodiment, the low-storage half-T-box white-box AES instance reduces the size of the lookup table for the first nine rounds by using a basic half-T table and rotational multiplexing relationships. It hides the direct relationship between input bytes and lookup indexes through an input combination encoding layer, fuses the current round key and the next round state encoding compensation through column constant groups, and completes the byte-level encoding output for the 10th round through the final round encoding table. These structures collectively achieve low-storage, dynamically updated, and non-explicitly exposed key white-box AES encryption.

[0044] This embodiment was prototype tested on an Ubuntu operating system and a general x86 architecture PC platform. The dynamic low-storage white-box AES encryption method of this invention was implemented using the C language. The test results are used to illustrate the storage overhead, generation overhead, and encryption latency performance of this invention under one prototype implementation condition, and do not limit the specific performance values ​​of this invention on other hardware platforms or software environments.

[0045] Performance test results show that, under prototype implementation conditions, the current low-storage half-T-box white-box AES instance generation time is approximately 0.258ms, which is in the sub-millisecond range; the instance runtime memory usage is approximately 14.41KB, less than 20KB. These results demonstrate that the present invention can complete dynamic white-box instance construction with low storage overhead and low instance generation latency, making it suitable for the lightweight deployment requirements of in-vehicle terminals.

[0046] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, or combinations made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A dynamic low-storage white-box AES encryption method for vehicle-to-everything (V2X) communication, characterized in that, Applied to vehicle-mounted terminals, the method includes: Step S1: Obtain the dynamic parameters corresponding to the current vehicle-to-everything (V2X) communication, including time slice number, link mode identifier, and regional grid identifier; Step S2: Input the dynamic parameters into the protected key area. Based on the pre-stored stub key and the dynamic parameters, the protected key area generates a short lifespan table generation seed corresponding to the current time window through a key derivation algorithm. Based on the short lifespan table, a temporary derivation session key and table generation parameters are generated from the seed. Step S3: Based on the session key and table generation parameters, construct a low-storage half-T box white-box AES instance corresponding to the current time window. The low-storage half-T box white-box AES instance includes a basic half-T table for rounds 1 to 9, an input combination coding layer, column constant groups and rotation multiplexing relationships, and a final round coding table for round 10. Step S4: After the low-storage half-T box white-box AES instance is constructed, clear the session key, temporary round key material and temporary data generated during the table generation process; Step S5: Call the low-storage half-T box white-box AES instance to perform block encryption on the vehicle network communication data. In the first to the ninth rounds, the half-T box lookup table and rotation multiplexing method are used to synthesize the column-level output. In the tenth round, the final round encoding table is used to process the byte-level output to obtain the encoded ciphertext. Step S6: When the time slice or communication context changes, regenerate the corresponding low-storage half-T box white-box AES instance.

2. The method according to claim 1, characterized in that: The root key is stored in the hardware security module, trusted execution environment, or other protected key area of ​​the vehicle terminal; the key derivation algorithm is a hash-based key derivation algorithm, and the dynamic parameters are encoded into fixed-length byte strings in a preset order before participating in key derivation; the time slice number is obtained by dividing a monotonic clock according to a preset time interval, which is 100 milliseconds to 500 milliseconds; the link mode identifier is used to distinguish different communication modes, communication objects, or session relationships; the area grid identifier is obtained by mapping the vehicle location, roadside unit coverage area, or preset road area.

3. The method according to claim 1, characterized in that: The basic semi-T table is used to store the AES byte replacement and column hybrid basic contribution corresponding to a single byte. Each table entry corresponds to an 8-bit input index and outputs a 32-bit column contribution value consisting of four bytes.

4. The method according to claim 1, characterized in that: The input combination coding layer sets different reversible codes for different byte positions to convert the current round input byte into a protected lookup index. The input combination coding layer of the first round integrates plaintext bytes, the influence of the initial round key, and input perturbation. The input combination coding layers of the second to ninth rounds are used to convert the previous round coding state into the current round lookup index.

5. The method according to claim 1, characterized in that: In rounds 1 to 9, the system selects four state bytes of the current column according to the row shifting rule, and after obtaining the lookup index through the input combination coding layer, accesses the same basic half-T table to obtain four 32-bit column contribution values. The four 32-bit column contribution values ​​participate in XOR synthesis by direct participation, 1-byte cyclic shift, 2-byte cyclic shift, and 3-byte cyclic shift, respectively, and are XORed with the corresponding column constant to obtain the 32-bit encoded state output of the column in the current round.

6. The method according to claim 5, characterized in that: The column constants are generated round by round and column by column, and are jointly derived from the current round key column, the next round state coding compensation, and the blinding perturbation. They are used to fuse the current round key in the column output synthesis stage and convert the current round column output into a coded state that can be processed in the next round.

7. The method according to claim 1, characterized in that: The 10th round does not include column mixing operations, and does not use the basic semi-T table, rotation multiplexing relation, and column constant group; the final round encoding table processes the 16-byte encoded state output of the 9th round, and completes the 9th round output encoding decoding, byte replacement, row shift mapping, 10th round key fusion, and output encoding to obtain the 16-byte encoded ciphertext.

8. The method according to claim 1, characterized in that: The storage overhead of the low-storage half-T box white box AES instance is no more than 20KB.

9. An electronic device, characterized in that, It includes a processor and a memory storing a computer program, wherein the processor executes the computer program to implement the method according to any one of claims 1 to 8.

10. A computer-readable storage medium having a computer program stored thereon, characterized in that, When the computer program is executed by a processor, it implements the method described in any one of claims 1 to 8.

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