Abstract: The authentication method is based on the exchange of text messages between an User electronic equipment, in the form of a mobile phone terminal, and an Intermediary electronic equipment, and between a Manager electronic equipment and an Intermediary electronic equipment; upon a request of authentication of a User by a Manager to an Intermediary, the Intermediary electronic equipment sends to the mobile phone terminal an authentication key by means of an encrypted text message; the mobile phone terminal decrypts the encrypted text message via a cryptography key, the cryptography key has been previously encrypted via a PIN and stored inside the mobile phone terminal; if the mobile phone terminal correctly replies to the encrypted text message by sending to the Intermediary electronic equipment an appropriate encrypted text message, authentication is successful; typically, SMS or MMS and asymmetric encryption are used for implementing this method.