History of all changes to the document. In terms of trust mechanism, QKFile is based on the underlying structure of quark blockchain, which keeps all the change history of the file, and is open, transparent, searchable and traceable, thus ensuring high transparency and high security. In terms of authority protection and granting mechanism, secure slices are used to store data, the holding relationship between users and files is verified by public key and private key signature technology, and the original token authorization mechanism is used to allow only authorized users to access data.