AUTHENTICATION PROTOCOL USING A ONE-TIME PASSWORD

Method of authenticating a client to a server, the client having beforehand registered on the server by storing therein a valid identifier (ID) and a hashed word (H0; Hn) generated by applying a hash function to a disposable random variable (RANDO; RANDn; Rn) possessed/known by both the client and the server and concatenated with a sequence (ISC0; ISCn) resulting from hashing the concatenation of a password (PWD) known from the client, said disposable random variable (RANDO; RANDn; Rn) and an initialization sequence (ISCinit) possessed by the client, comprising: a. the client requesting a connection session to the server by transmitting his/her/its identifier (ID); b. the server checking the existence of the identifier (ID) and allowing the client to continue the authentication process; c. the client transmitting a backhash (FSCn; Fn); d. the server applying to the concatenation of the hashed word (H0; Hn) and the backhash (FSCn; Fn) an inverse hash function obtained by algebraically solving said hash function; e. the server comparing the result of the inversion to the random variable (RANDO; RANDn; Rn) it possesses/knows; and f. if there is a match in the comparison of previous step e, authentication is successful for this connection session and the client is allowed to store on the server a new hashed word (Hn+1) corresponding to a different random variable (RANDn+1, Rn+1) and a possibly different password for the next connection session; otherwise, authentication fails.