A method for controlling access to a production system of a computer system by a user identified with said production system, the production system being not connected to an information system of said computer system, the information system comprising authentication means, the method being characterized in that it comprises the following steps: A) An initial phase of enrolling a user in the production computer system by means of a terminal comprising: - a) the supply to the user's terminal of an encrypted private key (Cph) associated with each user's account in the production system, - b) the transmission by the terminal of the encrypted private key (Cph) containing a private key (kpv) and the storing by the information system of said encrypted private key (Cph). B) Then, for each request for access to the production system by the user, by means of a station connected to the production system, a phase of authentication by the production system comprising: - the retrieval by the user's terminal of an image encryption code (QRCb) displayed on said station, comprising an encrypted data (Cph) associated with the user's account and decipherable by means of the associated private key (kpv) and stored in an encrypted form on the information system, - the connection of the terminal to the information computer system and the authentication of the user by said information system, - the transmission by said system to the user's terminal, of the encrypted private key (Cph) stored for the user account, - the decryption by the terminal of the private key encrypted (Cph) with a secret key (ks) in order to obtain the private key (kpv) allowing the decryption of the image encryption code retrieved by the terminal and obtain the password authorizing access to the user account of the production system. A) An initial phase of enrolling a user in the production computer system by means of a terminal comprising: - a) the supply to the user's terminal of an encrypted private key (Cph) associated with each user's account in the production system, - b) the transmission by the terminal of the encrypted private key (Cph) containing a private key (kpv) and the storing by the information system of said encrypted private key (Cph). - a) the supply to the user's terminal of an encrypted private key (Cph) associated with each user's account in the production system, - b) the transmission by the terminal of the encrypted private key (Cph) containing a private key (kpv) and the storing by the information system of said encrypted private key (Cph). B) Then, for each request for access to the production system by the user, by means of a station connected to the production system, a phase of authentication by the production system comprising: - the retrieval by the user's terminal of an image encryption code (QRCb) displayed on said station, comprising an encrypted data (Cph) associated with the user's account and decipherable by means of the associated private key (kpv) and stored in an encrypted form on the information system, - the connection of the terminal to the information computer system and the authentication of the user by said information system, - the transmission by said system to the user's terminal, of the encrypted private key (Cph) stored for the user account, - the decryption by the terminal of the private key encrypted (Cph) with a secret key (ks) in order to obtain the private key (kpv) allowing the decryption of the image encryption code retrieved by the terminal and obtain the password authorizing access to the user account of the production system. - the retrieval by the user's terminal of an image encryption code (QRCb) displayed on said station, comprising an encrypted data (Cph) associated with the user's account and decipherable by means of the associated private key (kpv) and stored in an encrypted form on the information system, - the connection of the terminal to the information computer system and the authentication of the user by said information system, - the transmission by said system to the user's terminal, of the encrypted private key (Cph) stored for the user account, - the decryption by the terminal of the private key encrypted (Cph) with a secret key (ks) in order to obtain the private key (kpv) allowing the decryption of the image encryption code retrieved by the terminal and obtain the password authorizing access to the user account of the production system.