Block chain-based data element auxiliary transaction method, device and system

The invention discloses a block chain-based data element auxiliary transaction method, device and system, and relates to the technical field of block chains. The method comprises the steps that according to metadata of multiple pieces of supply data and metadata of demand data in a block chain, the matching degree of each piece of supply data and the demand data is calculated, and target data providers are screened out; verifying whether the current supply data is the supply data of the target data provider based on the public key, the ciphertext of the current supply data and the signature of the ciphertext of the supply data, and if so, obtaining the current supply data from the current entry address through the one-time key; providing the current supply data to a data broker; when a matching condition is satisfied, determining a target transaction mode according to a privacy level of a target data provider obtained from the block chain; and uploading the target transaction mode to the block chain, so that