An embodiment encryption method, implemented by an electronic circuit including a first non-volatile memory, comprises the creation of one or more first pairs of asymmetrical keys, the first pair or each of the first pairs comprising first private and public keys, and, for the or at least one of the first pairs, storing the first public key in the first memory, receiving a second public key during a communication session, and forming a first symmetrical key from the first private key and the second public key, the first public key staying stored in the first memory after the communication session.