The invention provides an
implicit certificate key expansion method and device, and the method comprises the steps that a first user side generates a first symmetric key, a second symmetric key, a first key pair and a second key pair, and transmits a
certificate application request to a
certificate application registration center; the
certificate application registration center expands a first public key according to the first symmetric key and expands a second public key according to the second symmetric key to obtain a third public key and a fourth public key corresponding to each certificate index, and sends a certificate issuing request to a certificate
authorization center for each certificate index; and the certificate
authorization center generates a corresponding
implicit certificate according to the third public key corresponding to each certificate index, encrypts the corresponding
implicit certificate according to the fourth public key corresponding to each certificate index, and sends the encrypted implicit certificate corresponding to each certificate index to the certificate application registration center. According to the scheme, multiple implicit certificates can be obtained by sending the certificate application request once based on key extension, and the certificate generation efficiency is effectively improved.