US Patent 11438140 System and method for digital asset transfer

Methods, systems, and apparatus, including computer programs encoded on computer storage media, for digital asset buyback. One of the methods includes: obtaining a request for buying back a digital asset from a first blockchain account, the request comprising a quantity of the digital asset; identifying, based on the request, a blockchain contract that is deployed on the blockchain and that corresponds to the digital asset; generating a blockchain transaction for transferring the quantity of the digital asset from the first blockchain account to a second blockchain account associated with digital asset buyback, wherein the blockchain contract comprises a restriction prohibiting transfer of the digital asset out of the second blockchain account; and sending, to a blockchain node for adding to the blockchain, the blockchain transaction for transferring the quantity of the digital asset from the first blockchain account to the second blockchain account.