Abstract: The method of identity authentication at the user is provided to prove to the certificate authority that a key is owned by a user. The method can comprise selecting a certain number of keys from a set of keys of the user, obtaining a hash value of a correspondence between each key in the certain number of keys and a user identifier of the user respectively, and transmitting the obtained hash values to the certificate authority, and after receiving from the certificate authority a notification regarding a first subset of hash values, sending keys corresponding to the first subset of hash values as a first subset of keys to the certificate authority. The first subset of hash values can be selected by the certificate authority from the obtained hash values. Zero know ledge proof can be achieved with this technical solution.

Abstract: Disclosed are methods and apparatuses for electronic signature. The method for electronic signature comprises obtaining a hash value of a first key created for a user and a user identifier of the user, generating a key certificate of the first key based on the obtained hash value, the user identifier and a current key, recording the key certificate on a public medium, which public medium ensures that information published thereon is not tampered with, signing a file with the first key and recording a resulting file signature and the file on the public medium, and recording the first key on the public medium only after the file is already on the public medium. With the technical solution of the disclosure, a key can be effectively utilized.