The invention relates to an authentication method for authenticating a client device having an authentication token generated by means of a pseudo-homomorphic function and based on a secret element (PIN) known only by the client device, to a server, comprising: the generation (A1), by the client device, of proof of knowledge of the secret element based on a proof generation key masked with a first mask data item, said masked proof generation key being dependent on said secret element, the transmission to the server by the client device, of said generated proof of knowledge of the secret element (A2) and of the authentication token (J) masked using the mask data item (A3), the verification of the validity of the masked authentication token (A4) and of the validity of the proof of knowledge by the server (A6) by a zero-knowledge proof, proving the knowledge of said secret element by the client device without revealing it.