Recovering encrypted transaction information in blockchain confidential transactions

A system, comprising:

• a consensus node;
• a client node;
• wherein the consensus node is on a blockchain network, and the client node is off the blockchain network;
• the consensus node comprising:
• a consensus node computing device;
• and
• a consensus node storage device storing first computer-readable instructions that when executed by
• the consensus node computing device cause the consensus node computing device to perform operations of:
• receiving a content of a blockchain transaction of the client node, wherein the content of the blockchain transaction comprises:
• a first commitment value of a pre-transaction account balance of the client node and a first random number;
• a second commitment value of a transaction amount of the blockchain transaction and a second random number;
• a third commitment value of a post-transaction account balance of the client node;
• a first encrypted transaction information of both the pre-transaction account balance and the first random number, the first encrypted transaction information of both the pre-transaction account balance and the first random number encrypting both the pre-transaction account balance and the first random number using a secret key of the client node;
• a second encrypted transaction information of both the transaction amount of the blockchain transaction and the second random number, the second encrypted transaction information of both the transaction amount of the blockchain transaction and the second random number encrypting both the transaction amount of the blockchain transaction and the second random number using the secret key of the client node;
• and
• one or more zero-knowledge proofs of transaction data of the blockchain transaction;
• verifying that the blockchain transaction is valid based on the first commitment value, the second commitment value, the third commitment value, and the one or more zero-knowledge proofs of the transaction data of the blockchain transaction, wherein verifying that the blockchain transaction is valid comprises:
• verifying that the first commitment value, the second commitment value, and the third commitment value based on a cryptographic commitment scheme;
• and
• determining that the client node has enough account balance to transfer by verifying the one or more zero-knowledge proofs of the transaction data;
• in response to verifying that the blockchain transaction is valid, storing the first encrypted transaction information and the second encrypted transaction information on a blockchain of the blockchain network;
• receiving a request from the client node off the blockchain network for retrieving the first encrypted transaction information and the second encrypted transaction information stored on the blockchain;
• and
• sending the first encrypted transaction information of both the pre-transaction account balance and the first random number and the second encrypted transaction information of both the transaction amount of the blockchain transaction and the second random number to the client node;
• the client node comprising:
• a client node computing device;
• and
• a client node storage device storing second computer-readable instructions that when executed by the client node computing device cause the client node computing device to perform operations of:
• determining that the secret key is not in a local data storage of the client node;
• in response to determining that the secret key is not in the local data storage, recovering the secret key as a recovered secret key according to a threshold secret sharing scheme;
• and
• decrypting the first encrypted transaction information of both the pre-transaction account balance and the first random number and the second encrypted transaction information of both the transaction amount of the blockchain transaction and the second random number using the recovered secret key.