Private key retrieving method and device based on blockchain, and medium

The invention discloses a private key retrieving method and device based on a blockchain and a medium, and the method comprises the steps: obtaining a private key box corresponding to a user identifier from the blockchain according to the user identifier; collecting a first biological feature input by the user, and extracting first feature data through a biological feature extraction module; according to the first feature data, determining a data pair in compliance with a condition from the private key box corresponding to the user identifier; determining a first private key according to the data pair, and calculating a hash value of the first private key; and when it is determined that the hash value of the first private key is the same as the hash value of a pre-stored initial private key, determining that the first private key is the initial private key corresponding to the user identifier. According to the embodiment of the invention, the first private key is determined according to the first biological f