Patent ID: 8522027

Claim:
A method for authenticating an entity with a verifier, the entity possessing an identifier, the verifier possessing a private key/public key pair, the method comprising the steps: sending to the entity a first random number chosen by the verifier, encrypting a value (v) by the entity by means of the public key of the verifier, said value comprising the first random number and an authentication datum on which the identifier of the entity depends, in which the encryption complies with a public-key encryption scheme, called the modified El Gamal scheme, wherein: the step of encrypting the value (v) produces two elements T′ 1 =v⊕H(y w ), and T 2 ′=g w , where: H is an identity function or a hash function, and ⊕ an exclusive or operation, g is a generator of a group used by said scheme, y is the public key with which the private key x of the verifier is associated, said keys being such that y=g x , w is a second random number chosen by the entity, the step of decryption by the verifier of the two elements T 1 and T 2 computes T 1 ′⊕H(T 2 ′ x ) so as to provide said value (v), and sending in response, by the entity, of a message comprising said encrypted value, for authentication of said entity.