Computer-implemented method for protecting sensitive data in a transaction based on a smart contract deployed in a blockchain

A non-transitory computer-readable storage medium storing program instructions when executed by a computer system, the program instructions causing the computer system to perform a method for enhancing data confidentiality in a blockchain, the method comprising:

• maintaining the blockchain via a blockchain computer system, the blockchain computer system including a plurality of blockchain network nodes, the plurality of blockchain network nodes being connected to form a blockchain network, the blockchain being stored as copies of a distributed ledger on the blockchain network, the plurality of blockchain network nodes performing consensus-based verification to add a new block into the blockchain;
• coupling a first computer being to the blockchain as a first client device, wherein the first client device is configured to create a transaction specification, the transaction specification including an access condition for a protected transaction;
• coupling a plurality of second computers to the blockchain as a plurality of second client devices, wherein each one of the plurality of second client devices is configured to submit a sensitive transaction file to participate in the protected transaction;
• deploying a smart contract in the blockchain, the smart contract including a plurality of smart contract functions configured to protect the sensitive transaction files from being inappropriately modified or viewed;
• upon the sensitive transaction file being submitted by at least one of the plurality of second computers, via the at least one of the plurality of second computers, executing a first encryption on the submitted sensitive transaction file to generate a first encrypted sensitive transaction file C1, calculating a first hash value H1 for the sensitive transaction file and a submitting time of the sensitive transaction file, and calling a smart contract function of the smart contract to add the first hash value H1 as a block B1 into the blockchain;
• upon the first encrypted sensitive transaction file C1 being received by the first computer, via the blockchain computer system, performing a second encryption on the first encrypted sensitive transaction file C1 to generate a second encrypted sensitive transaction file C2, calculating a second hash value H2 for the first encrypted sensitive transaction file C1 and a receiving time of the first encrypted sensitive transaction file C1, and calling the smart contract function to add the second hash value H2 as a block B2 into the blockchain;
• upon the access condition for the protected transaction being met, via the blockchain computer system, performing a decryption on the second encrypted sensitive transaction file C2 to obtain a decrypted sensitive transaction file, verifying the decryption by comparing the decrypted sensitive transaction file against the first encrypted sensitive transaction file C1, and upon determining that the decrypted sensitive transaction file matches with the first encrypted sensitive transaction file C1, sending to the at least one second computer a request for opening the decrypted sensitive transaction file;
• upon receiving the request, via the at least one second computer, performing a decryption on the decrypted sensitive transaction file to generate an opened sensitive transaction file, comparing a new hash value calculated for the opened sensitive transaction file and the submitting time against the first hash value H1 in the block B1, and upon determining that the new hash value matches with the first hash value H1, calculating a third hash value H3 for the opened sensitive transaction file and the opening time, and calling the smart contract function to add the third hash value H3 as a block B3 into the blockchain;
• via the blockchain computer system, performing a three-step verification for the sensitive transaction file, including:
• a first verification based on the first hash value H1 in the block B1, to verify whether the sensitive transaction file was submitted at a correct time,
• a second verification based on the second hash value H2 in the block B2, to verify whether the sensitive transaction file was received at a correct time, and
• a third verification based on the third hash value H3 in the block B3, to verify whether the sensitive transaction file was opened at a correct time;
• when any of the first, second, and third verifications obtains a negative result, marking the sensitive transaction file as having been inappropriately modified or viewed, and when the first, second, and third verifications all obtain positive results, determining that the sensitive transaction file was not inappropriately modified or viewed, and generating a digital signature based on the first hash value H1, the second hash value H2, and the third hash value H3;
• and
• upon the digital signature being generated for the sensitive transaction file, via the blockchain computer system, calling the smart contract function to add the sensitive transaction file as a block B4 into the blockchain.