A blockchain-based encryption and decryption method for bidding documents

Abstract

The application relates to the technical field of blockchains, and particularly discloses a bidding file encryption and decryption method based on a blockchain, which comprises the following steps: performing hash calculation on the spliced calculation parameters to obtain an opening anchor point, and calculating a challenge value based on the opening anchor point and a verifiable delay function; encrypting the bidding file based on a symmetric key to obtain inner-layer ciphertext and calculating an integrity identifier; obtaining time-lock ciphertext based on the challenge value and the symmetric key, and obtaining a content identifier; obtaining the symmetric key based on the time-lock ciphertext and the challenge value, and decrypting the inner-layer ciphertext based on the symmetric key to obtain bidding file plaintext. The application combines time locks and on-chain parameters to generate and restore keys, realizes the whole process without relying on any single institution to save the keys, avoids centralized hosting risks, and ensures the safety and controllability of bidding data.

Description

Technical Field

[0001] This invention relates to the field of blockchain technology, and specifically to a blockchain-based method for encrypting and decrypting bidding documents. Background Technology

[0002] Bidding documents are crucial written materials submitted by both the tendering party and the bidders in engineering construction, material procurement, and service outsourcing activities, used for evaluation and determining the successful bidder. Their content typically includes a project overview, technical requirements, commercial terms, and evaluation methods. The tender documents are prepared by the tendering party, clearly defining the bidding conditions and evaluation criteria; the bid documents are prepared by the bidders based on the tender documents, explaining their qualifications, pricing, and technical solutions. The completeness, accuracy, and legality of the bidding documents directly affect the fairness of the evaluation and the smooth implementation of the project.

[0003] In blockchain-based bidding document encryption and decryption schemes, documents are typically encrypted and stored in trusted on-chain or off-chain storage during the bidding stage, and can only be decrypted during the bid opening to ensure fairness and confidentiality. However, in practice, centralized or semi-centralized key management methods are often relied upon, such as having the bidding party or a specific third party hold the private keys in escrow. While this design theoretically simplifies access control, it introduces a single point of failure risk in real-world environments: if the key escrow provider experiences internal leakage, is attacked, or loses the key due to mismanagement, all encrypted files may be prematurely cracked or permanently rendered undecryptable. Summary of the Invention

[0004] The purpose of this invention is to provide a blockchain-based method for encrypting and decrypting bidding documents, thereby solving the aforementioned technical problems.

[0005] The objective of this invention can be achieved through the following technical solutions:

[0006] A blockchain-based method for encrypting and decrypting bidding documents includes the following steps:

[0007] The calculation parameters are obtained based on the smart contract. The concatenated calculation parameters are hashed to obtain the bidding anchor point. The challenge value is calculated based on the bidding anchor point and the verifiable delay function.

[0008] The tender document is encrypted using a pre-generated symmetric key to obtain inner ciphertext, and an authentication tag is output during the encryption process. An integrity identifier is calculated based on the inner ciphertext and the authentication tag.

[0009] The time-lock ciphertext is obtained based on the challenge value and symmetric key, and the content identifier generated by the hash encoding of the time-lock ciphertext and the hash encoding of the inner ciphertext is obtained through IPFS.

[0010] After the bid opening time arrives, a symmetric key is obtained based on the time-locked ciphertext and the challenge value. The inner ciphertext is then decrypted using the symmetric key to obtain the plaintext of the bid document.

[0011] As a further aspect of the present invention: the process of obtaining calculation parameters includes:

[0012] The calculation parameters include the on-chain state summary, the tender identifier, and the on-chain address of the smart contract;

[0013] A smart contract is created and deployed on the blockchain. After the deployment transaction is confirmed on the chain, the smart contract reads the hash value of the most recent block from the accessible context and uses it as an on-chain state summary. It also reads the on-chain address of the smart contract from the same context. When it receives a transaction that initiates a tender, it parses the tender identifier from the character sequence carried by the transaction.

[0014] As a further aspect of the present invention: the process of calculating the challenge value includes:

[0015] Obtain the calculation parameters, perform a hash operation on the three calculation parameters concatenated in a predetermined order to obtain the opening anchor point, input the opening anchor point into Wesolowski to verify the challenge generation process of the delay function, obtain the challenge value based on the hash function and record it on the chain.

[0016] As a further aspect of the present invention: the calculation integrity identifier includes:

[0017] The pre-generated symmetric key is concatenated with the random number string B generated by the bidder through the kernel entropy pool to obtain the input parameters of the AES-GCM algorithm. The AES-GCM algorithm encrypts the bid document based on the input parameters to obtain the inner ciphertext and outputs an authentication tag during the encryption process. The inner ciphertext and the authentication tag are concatenated as input, and the hash result is calculated based on the Keccak algorithm. The hash result is used as the integrity identifier.

[0018] As a further aspect of the present invention, the process of generating a symmetric key includes:

[0019] The bidder generates a random number string A through the kernel entropy pool, concatenates the random number string A to the beginning of the bidder's private key to obtain input data, performs operations on the input data based on the VRF algorithm to obtain random fragments and corresponding verifiable proofs, and inputs the random fragments into the key derivation function to generate a symmetric key with a byte length that meets the preset requirements.

[0020] As a further aspect of the present invention: the process of obtaining the content identifier includes:

[0021] The challenge value is input into the hash function to obtain the initial byte sequence, and the initial byte sequence is mapped to an element in the RSA group. On this element, a continuous squaring operation is performed based on the Wesolowski verifiable delay function to obtain the final calculation result.

[0022] The final calculation result is input into the hash function, and the output is a fixed-length byte sequence as an encryption mask. The symmetric key and the encryption mask are XORed bitwise to obtain the time-locked ciphertext.

[0023] The inner ciphertext and time-lock ciphertext are uploaded to IPFS respectively, and the corresponding content identifiers are obtained. Each content identifier comes from the hash encoding of the uploaded content. The uploaded content consists of the inner ciphertext and the time-lock ciphertext.

[0024] As a further aspect of the present invention: the process of obtaining the plaintext of the tender document includes:

[0025] Participants read the registered timelock ciphertext and challenge value from the blockchain, convert the challenge value into an initial byte sequence using a hash function and map it to element C1 in the RSA group, perform continuous square operations on element C1 based on the Wesolowski verifiable delay function to obtain intermediate result C2 and generate a proof file C3 for verifying intermediate result C2, and perform a bitwise XOR operation between intermediate result C2 and timelock ciphertext to obtain the symmetric key;

[0026] AES-GCM decryption processes ciphertext blocks sequentially after loading the symmetric key and the initial random number required for decryption, obtaining the plaintext of the tender document and outputting the authentication tag C4.

[0027] The generated authentication tag C4 after decryption is compared with the integrity identifier. Only when the comparison matches is the plaintext of the tender document output completed.

[0028] The beneficial effects of this invention are:

[0029] 1. This invention generates a symmetric key during the bidding stage and combines it with a verifiable delay function and a challenge value recorded on the chain, so that the key cannot be derived or obtained before the bidding time, effectively preventing the possibility of premature decryption. This timed decryption mechanism does not rely on a centralized key management method, structurally reducing the risk of files being published prematurely or permanently unable to be decrypted due to key leakage or management errors.

[0030] 2. This invention generates an integrity identifier during the encryption process and verifies it through an authentication tag after decryption, ensuring that the plaintext of the output bid document is consistent with the original document submitted by the bidder. This design effectively prevents the document from being tampered with during on-chain or off-chain storage and transmission, ensuring the authenticity and verifiability of the bid opening results;

[0031] 3. This invention uploads the inner ciphertext and the time-locked ciphertext to trusted storage separately and associates them based on content identifiers, forming a separate management mode for keys and file data. The key required for decryption can only be recovered after the predetermined delay calculation is completed, thereby maintaining high security and reliability throughout the entire process of data storage, transmission and decryption. Attached Figure Description

[0032] The invention will now be further described with reference to the accompanying drawings.

[0033] Figure 1 This is a flowchart illustrating a blockchain-based method for encrypting and decrypting bidding documents according to the present invention. Detailed Implementation

[0034] 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 embodiments of the present invention, and not all embodiments. 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.

[0035] Please see Figure 1 As shown, this invention is a blockchain-based method for encrypting and decrypting bidding documents, comprising the following steps:

[0036] Step 1: Obtain the calculation parameters based on the smart contract, perform hash calculation on the concatenated calculation parameters to obtain the bidding anchor point, and calculate the challenge value based on the bidding anchor point and the verifiable delay function;

[0037] In a preferred embodiment of the present invention, the process of obtaining calculation parameters includes:

[0038] A smart contract that can participate in the bidding process is built on the blockchain. When the participants deploy the smart contract, they submit the deployment operation to the blockchain network. Multiple nodes in the network verify the operation and write it into the blockchain ledger. Once the deployment transaction is confirmed by the blockchain, the smart contract will have a unique address on the blockchain. This address cannot be repeated or arbitrarily changed across the entire network, so it can be used as a key parameter to identify the smart contract.

[0039] At this point, the smart contract can read the running status information of its chain, including the hash value of the most recently generated block. This hash value is obtained by cryptographic hashing the transaction data, timestamp, previous block hash, and other on-chain state information within the block. Due to the consensus mechanism of the blockchain, this hash value is unique across the entire network and the original data cannot be reversed. Therefore, it can be used to reflect the state of the chain at a certain moment. In this invention, this hash value is used as an on-chain state digest.

[0040] When the bidding process begins, the initiator sends a specific transaction to the smart contract. This transaction contains identifying information related to the bidding activity. This identifying information is usually a string of information manually set during the initiation phase. By parsing the raw data contained in this transaction, the smart contract can separate and extract this identifying information from other irrelevant information.

[0041] After the above steps, three core calculation parameters can be obtained: on-chain state summary, tender identifier, and on-chain address of smart contract.

[0042] In a preferred embodiment, the process of calculating the challenge value includes:

[0043] The three calculation parameters are concatenated in a pre-agreed order to ensure that the results of the same set of parameters are consistent across the entire network, and that different results are obtained due to different orders.

[0044] A hash operation is performed on the concatenated data. The purpose of the hash algorithm is to map data of arbitrary length to a digest value of fixed length and irreversible. This digest value is called the opening anchor in this invention. Since the input data contains the on-chain state digest generated in real time, the result of the opening anchor generated at different times will inevitably be different, ensuring unpredictability.

[0045] The opening anchor is considered as a fixed-length byte sequence, which can be mapped to a large integer range in mathematics. This mapping is definite and unique. Through a pre-agreed hash calculation, the large integer is further processed into the initial challenge data. The purpose of this step is to break down the structural features that the opening anchor may originally have, so that the generated results are evenly distributed and difficult to infer the input value through reverse analysis.

[0046] Mapping this initial challenge data to a predefined mathematical group, such as a multiplication group with a specific order and operational rules, ensures that the subsequent calculation process is mathematically difficult to derive in advance. On the elements of this group, continuous exponential operations are performed according to the pre-set number of calculations and calculation methods. The result of each step depends on the result of the previous step, so the final value cannot be obtained directly by skipping steps or pre-calculating.

[0047] The group element results obtained from continuous calculations are hashed again and mapped to a fixed-length byte sequence. This byte sequence is the challenge value in this invention. The challenge value is characterized by the fact that it cannot be obtained in advance before the complete calculation steps are performed, but anyone can verify its correctness after the specified calculation is completed. The generated challenge value will be recorded on the blockchain to ensure that it is verifiable and tamper-proof across the entire network.

[0048] Step 2: Encrypt the tender document using the pre-generated symmetric key to obtain the inner ciphertext and output the authentication tag during the encryption process. Calculate the integrity identifier based on the inner ciphertext and the authentication tag.

[0049] In another preferred embodiment of the present invention, the calculation of the integrity identifier includes:

[0050] After pre-generating the symmetric key, a random number string B also needs to be generated for encryption. This is also obtained through the kernel entropy pool, which introduces new randomness into the encryption process.

[0051] The symmetric key and the random number string B are concatenated in a pre-set order to obtain the input parameters of the AES-GCM algorithm. AES-GCM is a mode that combines a block cipher algorithm with an authentication mechanism. Its working principle is to generate an authentication tag related to the encrypted data through the GHASH function while performing AES symmetric encryption, which is used to verify whether the data has been tampered with during transmission or storage.

[0052] When encrypting the tender document, the AES part will divide the input parameters and plaintext file data into blocks and perform a series of substitution and permutation operations to obtain the encrypted inner ciphertext; at the same time, the GCM mode will perform finite field multiplication operations on the ciphertext, key, random number string B and other information involved in the encryption process to obtain an authentication tag. This tag can uniquely correspond to the current encryption result and input conditions.

[0053] After encryption, the inner ciphertext and the authentication tag are concatenated into a complete set of data, which is then input into the Keccak algorithm for hashing. Keccak is a hash algorithm based on a permutation and absorption-extrusion structure. It absorbs the input data into blocks into an internal state matrix, completely disassembles the original data through multiple rounds of nonlinear permutation and hybrid operations, and then generates a fixed-length hash value through the extrusion stage. Due to the avalanche effect of Keccak, even the slightest change in the input data will result in a completely different output.

[0054] In this invention, the hash result calculated by the Keccak algorithm is used as an integrity identifier to compare and verify the decrypted file during the bid opening and decryption stage, ensuring that the file has not been tampered with and is consistent with the original file submitted by the bidder.

[0055] It should be noted that the process of generating a symmetric key includes:

[0056] A random number string A is obtained from the kernel entropy pool on the bidder's local machine. The entropy pool generates high-quality random numbers by collecting information on unpredictable events generated during system operation (such as hardware interrupt time, input / output delay, system noise, etc.). Therefore, the random number string A has strong unpredictability.

[0057] This random number string A is appended to the beginning of the bidder's private key to form a new input data. This appending method makes the input data contain both random components from the entropy pool and the bidder's unique private key information, making the key generation process highly bound to the bidder.

[0058] The input data is processed based on the VRF (Verifiable Random Function) algorithm. The principle of the VRF algorithm is to ensure a deterministic mapping between the input and the output, while making it impossible to predict the output without knowing the private key, and to generate a verifiable proof file to prove that the output is calculated by a specific input and private key.

[0059] In this invention, a random segment and a corresponding verifiable proof are obtained through VRF algorithm. The random segment is generated through elliptic curve operations and hash mapping, which ensures the randomness and uniqueness of the result. The verifiable proof can be used to confirm the authenticity of the random segment when needed later. The random segment is input into the key derivation function, which transforms the input random segment into an output sequence that meets the preset byte length requirement through repeated hash calculations and byte expansion. This output sequence is the symmetric key used in the subsequent encryption process.

[0060] Step 3: Obtain the time lock ciphertext based on the challenge value and symmetric key, and obtain the content identifier generated by the hash encoding of the time lock ciphertext and the hash encoding of the inner ciphertext through IPFS;

[0061] In another preferred embodiment of the present invention, the process of obtaining the content identifier includes:

[0062] The challenge value obtained in the previous step is input into a hash function for calculation. The purpose of the hash function is to map an input of arbitrary length to an output of fixed length that is difficult to reverse-engineer. Due to its avalanche effect, even if the input changes by a tiny amount, the output result will be completely different. In this invention, hashing the challenge value can eliminate the structural regularity that may exist in its generation process, ensuring the uniformity and unpredictability of the input for subsequent calculations. After hashing, a fixed-length initial byte sequence is obtained. This byte sequence is then mapped to elements in an RSA group. The RSA group is composed of a multiplicative group under a large integer modulus. Its security depends on the difficulty of factoring large integers. The purpose of mapping the initial byte sequence to RSA group elements is to transform the original linear data space into a mathematical structure with complex computational characteristics, so that the results of subsequent calculations cannot be obtained through simple analysis or pre-calculation.

[0063] After obtaining the RSA group element, a series of squaring operations are performed on that element based on the Wesolowski verifiable delay function to obtain the final calculation result. The principle of the Wesolowski verifiable delay function is to perform a certain number of exponentiation operations on a specified mathematical group, where the result of each operation depends on the previous operation, and intermediate steps cannot be skipped for pre-calculation. Therefore, in actual operation, a certain amount of real time is required to obtain the final result. In this invention, the final calculation result is obtained in this way, ensuring that the intermediate data required for combining with the symmetric key cannot be obtained in advance before the bidding time, thereby achieving a time-locking effect.

[0064] The final calculation result is input into a hash function to obtain a fixed-length byte sequence. The purpose of this process is to map the complex group operation result into a regular mask data that facilitates subsequent bitwise operations. The hash function here also serves to break down the data pattern, making the relationship between the output mask and the original operation result irreversible.

[0065] Then, the previously generated symmetric key is XORed with the mask. XOR is a common basic operation of symmetric encryption. Its characteristic is that the original data can be restored by XORing the same mask again. Therefore, the time-locked ciphertext obtained by XORing the mask with the symmetric key cannot recover the symmetric key without the mask. The generation of the mask depends on the time-consuming delay function operation, thus binding the time when the symmetric key can be obtained to the delay operation process.

[0066] The encrypted inner ciphertext and time-lock ciphertext are uploaded to the IPFS storage system respectively. IPFS is a distributed file storage and transmission protocol that hashes the content during file upload. The resulting hash value is the unique content identifier of the file. This identifier corresponds one-to-one with the file content, and any modification will result in a change to the identifier. In this invention, the inner ciphertext and time-lock ciphertext are uploaded separately to obtain the corresponding content identifiers. These identifiers are then used to achieve unique file location and decentralized storage, thereby ensuring that encrypted data and its time-lock information can be accurately retrieved and obtained when needed.

[0067] Step 4: After the bid opening time arrives, obtain the symmetric key based on the time lock ciphertext and the challenge value, and decrypt the inner ciphertext based on the symmetric key to obtain the plaintext of the bid document.

[0068] In another preferred embodiment of the present invention, the process of obtaining the plaintext of the tender document includes:

[0069] When the bidding time arrives, participants first read the time lock ciphertext and challenge value that were registered during the bidding stage from the blockchain. These two data are necessary conditions for unlocking the bid documents. The read challenge value is input into a hash function for calculation to obtain an initial byte sequence of fixed length. This step is to break down the original pattern of the challenge value and transform it into uniformly distributed and irreversible input data.

[0070] The initial byte sequence is mapped to an element C1 in the RSA group. The RSA group is composed of a multiplication group of modulo large integers. Its mathematical properties ensure that the operation of the element cannot be reversed in a short time, thus making the subsequent delayed operation safe.

[0071] After obtaining element C1, a continuous squaring operation is performed on this element based on the Wesolowski verifiable delay function. This operation requires the exponential operation to be performed a set number of times in sequence. The result of each step depends on the calculation of the previous step. Therefore, it is not possible to obtain the result in advance by skipping steps. Finally, an intermediate result C2 is obtained, and a proof file C3 is generated to verify the correctness of C2 when necessary.

[0072] The intermediate result C2 is XORed with the time-lock ciphertext bitwise. The characteristic of the XOR operation is that the original data can be recovered by XORing the same data again. Therefore, the symmetric key originally used for encryption can be obtained by XORing C2 with the time-lock ciphertext.

[0073] After obtaining the symmetric key, the key and the initial random number used in the encryption phase are loaded, and the AES-GCM decryption process begins. AES-GCM is a mode that combines AES symmetric decryption with integrity verification. During decryption, reverse substitution and permutation operations are performed block by block according to the order of the ciphertext groups to gradually restore the original tender document data. During the decryption process, the GCM mode generates an authentication tag C4. This tag is obtained by performing finite field operations based on the key, random number, and ciphertext while decrypting the data and is used to confirm the integrity of the decryption result.

[0074] The generated authentication tag C4 is compared with the integrity identifier recorded in the bidding stage. If the two are completely consistent, it means that the plaintext of the decrypted bid document is consistent with the original file before encryption and has not been tampered with. Only then is the plaintext of the bid document output completed. If they are inconsistent, the plaintext is rejected to prevent the tampered data from being received incorrectly.

[0075] The foregoing has provided a detailed description of one embodiment of the present invention, but this description is merely a preferred embodiment and should not be construed as limiting the scope of the invention. All equivalent variations and modifications made within the scope of the present invention should still fall within the scope of the present invention.

Claims

1. A blockchain-based method for encrypting and decrypting bidding documents, characterized in that, Includes the following steps: The calculation parameters are obtained based on the smart contract. The concatenated calculation parameters are hashed to obtain the bidding anchor point. The challenge value is calculated based on the bidding anchor point and the verifiable delay function. The tender document is encrypted using a pre-generated symmetric key to obtain inner ciphertext, and an authentication tag is output during the encryption process. An integrity identifier is calculated based on the inner ciphertext and the authentication tag. The time-lock ciphertext is obtained based on the challenge value and symmetric key, and the content identifier generated by the hash encoding of the time-lock ciphertext and the hash encoding of the inner ciphertext is obtained through IPFS. After the bid opening time arrives, the symmetric key is obtained based on the time lock ciphertext and the challenge value. The inner ciphertext is then decrypted using the symmetric key to obtain the plaintext of the bid document. The process of obtaining calculation parameters includes: The calculation parameters include the on-chain state summary, the tender identifier, and the on-chain address of the smart contract; A smart contract is created and deployed on the blockchain. After the deployment transaction is confirmed on the chain, the smart contract reads the hash value of the most recent block from the accessible context and uses it as an on-chain state summary. It also reads the on-chain address of the smart contract from the same context. When it receives a transaction that initiates a tender, it parses the tender identifier from the character sequence carried by the transaction.

2. The blockchain-based method for encrypting and decrypting bidding documents according to claim 1, characterized in that, The process of calculating the challenge value includes: Obtain the calculation parameters, perform a hash operation on the three calculation parameters concatenated in a predetermined order to obtain the opening anchor point, input the opening anchor point into Wesolowski to verify the challenge generation process of the delay function, obtain the challenge value based on the hash function and record it on the chain.

3. The blockchain-based method for encrypting and decrypting bidding documents according to claim 2, characterized in that, Computational integrity identifiers include: The pre-generated symmetric key is concatenated with the random number string B generated by the bidder through the kernel entropy pool to obtain the input parameters of the AES-GCM algorithm. The AES-GCM algorithm encrypts the bid document based on the input parameters to obtain the inner ciphertext and outputs an authentication tag during the encryption process. The inner ciphertext and the authentication tag are concatenated as input, and the hash result is calculated based on the Keccak algorithm. The hash result is used as the integrity identifier.

4. The blockchain-based method for encrypting and decrypting bidding documents according to claim 3, characterized in that, The process of generating a symmetric key includes: The bidder generates a random number string A through the kernel entropy pool, concatenates the random number string A to the beginning of the bidder's private key to obtain input data, performs operations on the input data based on the VRF algorithm to obtain random fragments and corresponding verifiable proofs, and inputs the random fragments into the key derivation function to generate a symmetric key with a byte length that meets the preset requirements.

5. The blockchain-based method for encrypting and decrypting bidding documents according to claim 4, characterized in that, The process of obtaining the content identifier includes: The challenge value is input into the hash function to obtain the initial byte sequence, and the initial byte sequence is mapped to an element in the RSA group. On this element, a continuous squaring operation is performed based on the Wesolowski verifiable delay function to obtain the final calculation result. The final calculation result is input into the hash function, and the output is a fixed-length byte sequence as an encryption mask. The symmetric key is XORed with the encryption mask bit by bit to obtain the time-locked ciphertext. The inner ciphertext and time-lock ciphertext are uploaded to IPFS respectively, and the corresponding content identifiers are obtained. Each content identifier comes from the hash encoding of the uploaded content. The uploaded content consists of the inner ciphertext and the time-lock ciphertext.

6. The blockchain-based method for encrypting and decrypting bidding documents according to claim 5, characterized in that, The process of obtaining the plaintext of the tender documents includes: Participants read the registered timelock ciphertext and challenge value from the blockchain, convert the challenge value into an initial byte sequence using a hash function and map it to element C1 in the RSA group, perform continuous square operations on element C1 based on the Wesolowski verifiable delay function to obtain intermediate result C2 and generate a proof file C3 for verifying intermediate result C2, and perform a bitwise XOR operation between intermediate result C2 and timelock ciphertext to obtain the symmetric key; AES-GCM decryption processes ciphertext blocks sequentially after loading the symmetric key and the initial random number required for decryption, obtaining the plaintext of the tender document and outputting the authentication tag C4. The generated authentication tag C4 after decryption is compared with the integrity identifier. Only when the comparison matches is the plaintext of the tender document output completed.

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