Abstract: Blockchain-based transaction methods, apparatuses and systems are provided. A transaction party invokes a smart contract in a blockchain system to register a digital identity on a blockchain for a digital object in the blockchain system and to write an owner identity of the digital object into a digital identity document of the digital object. If one or more transaction counterparties want to obtain ownership of the digital object, they can invoke the smart contract in the blockchain system to initiate a request of a transaction, further invoke the smart contract in the blockchain system to complete a transaction, determine a new owner of the digital object, and update the owner identity of the digital object on the blockchain.

Abstract: One or more embodiments of the present specification provide privacy protection-based multicollinearity detection methods, apparatuses, and systems. Data alignment is performed by a member device on respective local feature data with other member devices to construct a joint feature matrix. Privacy protection-based multi-party matrix multiplication computation is performed to compute a product matrix of a transposed matrix of the joint feature matrix and the joint feature matrix. An inverse matrix of the product matrix is determined based on respective submatrices of the product matrix. A variance inflation factor of each attribute feature is determined by the member device with the other member devices using respective submatrices of the inverse matrix and the respective local feature data. Multicollinearity is determined by the member device with the other member devices based on fragment data of the variance inflation factor of each attribute feature.

Abstract: One or more embodiments of the present specification provide disk storage-based data reading methods, apparatuses, and systems. A data reading instruction sent by a client device is received. The data reading instruction includes a service attribute. Location information corresponding to the service attribute is obtained from a pre-stored index table. The location information includes block heights and offsets of data blocks in which one or more data records are located. A block height sequence is generated by sequentially arranging the block heights. Mutually exclusive continuous block height intervals are determined from the block height sequence. One or more target data blocks are read corresponding to a block height interval from a disk. The one or more data records are obtained by querying the one or more target data blocks based on the location information, and returned to the client device.

Abstract: Blockchain-based transaction methods, apparatuses and systems are provided. A transaction party invokes a smart contract in a blockchain system to register a digital identity on a blockchain for a digital object in the blockchain system and to write an owner identity of the digital object into a digital identity document of the digital object. If one or more transaction counterparties want to obtain ownership of the digital object, they can invoke the smart contract in the blockchain system to initiate a request of a transaction, further invoke the smart contract in the blockchain system to complete a transaction, determine a new owner of the digital object, and update the owner identity of the digital object on the blockchain.