Method for Authenticating a Client Device to a Server Using a Secret Element

System comprising:

• at least one client device and a client device authentication server using a secret element known only by the client device, said client device being configured to:
• hold an authentication token generated by means of a pseudo-homomorphic function and based on said secret element,
• generate a proof of knowledge of the secret element based on a proof generation key masked with a first mask data item, said first mask data item being a non-public, random data item known only by the client device and said masked proof generation key being dependent on said secret element,
• transmit to the server said proof of knowledge of the secret element generated,
• transmit to the server the authentication token masked using the first mask data item, said server being configured to:
• receive said proof of knowledge of the secret element, generated based on the proof generation key masked with a first mask data item, and transmitted by the client device,
• receive the authentication token masked using the first mask data item,
• verify the validity of the masked authentication token received,
• verify the validity of the proof of knowledge by a zero-knowledge proof, proving the knowledge of said secret element by the client device without revealing it.