Method for controlling access to a production system of a computer system not connected to an information system of said computer system

Method (M) for controlling access to a production system (SIP) of a computer system by a user identified with said production system (SIP), the production system not being connected to an information system (SIC) of said computer system, the information system (SIC) comprising authentication means, the method comprising the following steps:

• A) an initial phase of enrolling a user in the production computer system (SIP) by means of a terminal (1) comprising:
• a) the furnishing to the user's terminal of an encrypted private key (Cph) associated with each account of the user in the production system (SIP),
• b) the transmission by the terminal (1) of the encrypted private key (Cph) containing a private key (kpv) and the storing by the information system (SIC) of said encrypted private key (Cph);
• B) then, for each request for access to the production system (SIP) by the user, by means of a station (P) linked to the production system, a phase for authentication by the production system (SIP) comprising:
• the recovery by the terminal (1) of the user of an image encryption code (QRCb) displayed on said station (P), comprising a piece of encrypted data (Cph) associated with the account of the user and that can be decrypted by means of the associated private key (kpv) and stored in encrypted form in the information system (SIC),
• the linking of the terminal (1) to the information computer system (SIC) and the authentication of the user by said information system (SIC),
• the transmission by said system (SIC) to the user's terminal (1) of the stored encrypted private key (Cph) for the user account, and
• the decrypting by the terminal (1) of the encrypted private key (Cph) with a secret key (ks) so as to obtain the private key (kpv) that makes it possible to decrypt the image encryption code recovered by the terminal (1) and to obtain the password (PWD) authorizing access to the user account of the production system.