The method includes generating an additional block for expanding a blockchain structure, which includes the data to be stored and is intended to be linked bidirectionally to the last block of the blockchain structure; calculating a first check value of the last block for bidirectionally linking the additional block to the last block of the blockchain structure; calculating a check value of the additional block for bidirectionally linking the additional block to the last block of the blockchain structure; adding the first check value of the last block to the last block and; adding the check value of the additional block to the additional block.