Patent ID: 7769999

Claim:
A method for remote password based authentication using smart cards for accessing a communications network, the method comprising: generating, by an authentication server, a first encrypted user message g ID|PW , by encrypting a predetermined system parameter, g, using a first hash function, h1( . . . ), and an inverse function of a second hash function, h2( . . . ), with a concatenation of a predetermined security key x and a user ID as input for the first hash function and a user password PW as an input for the inverse function of the second hash function according to g ID|PW =g h 1 (ID∥x)·h 2 −1 (PW) mod p; sending, by the authentication server, the first encrypted user message and predetermined system parameters, g, p to be stored in a smart card used by the user, that enable the smart card to send a login request message when the user uses a remote terminal to login to the communications network by entering the user ID and the user password PW, wherein the login request message contains a first value, C1 and a second value, C2, the C1 being generated according to C 1 =g r mod p, and C2 being generated according to C 2 =H(ID, T, k) mod p, wherein H( . . . ) is a third hash function, inputs of which include a time-stamp T representing a current time of the terminal and a second encrypted user message, k, which is generated according to k=g ID|PW r·h 2 (PW) mod p, where r is a random number; receiving, by the authentication server, the login request message containing the first value and the second value; and verifying, by the authentication server, a predetermined relationship between the second value and a third value, wherein the third value is generated using the third hash function having at least one input based on a function of the first value and the first hash function which uses the security key as an input.