Method for configuring access to fallback communication services and associated system

A method for configuring access by a user to fallback communication services accessible via a transport network, the access to the fallback communication services requiring an authentication, the method comprising:

• sending, by an application client hosted on a user equipment, an authentication request to an identity management server;
• in the event of rejection of the authentication request by the identity management server:
• allocating, by the identity management server, a unique fallback identifier to the user and sending, by the identity management server, the unique fallback identifier to the application client;
• sending, by the application client, a request for fallback user profile comprising the unique fallback identifier to a configuration management server and receiving, by the application client, a corresponding fallback user profile sent by the configuration management server, the user then being authenticated in fallback mode;
• sending, by the application client, a request for fallback multimedia group profiles comprising the unique fallback identifier to a multimedia group management server and receiving, by the application client, at least one corresponding fallback multimedia group profile sent by the multimedia group management server;
• sending, by the application client, a request for fallback multimedia group encryption keys and private communications encryption keys comprising the unique fallback identifier to an encryption keys management server and receiving, by the application client, at least one fallback multimedia group encryption key and at least one corresponding private communications encryption key sent by the encryption keys management server;
• once the application client has received the corresponding fallback user profile, the at least one corresponding fallback multimedia group profile, the at least one fallback multimedia group encryption key and the at least one corresponding private communications encryption key, accessing, by the user, the fallback communication services.