Patent ID: 8738900

Claim:
A method for secure communications in a telecommunications network, the network comprising a group of servers S i (where i=1, 2, . . . , p, and p is a strictly positive integer), referred to as Authorization Servers, the method comprising, for a transaction between an entity A and an entity B of the network, the following steps: a) the entity A sends to one of the Authorization Servers S i an authorization request (REQ) in which the entity A identifies and authenticates itself as the holder of an identifier ID A ; b) the entity A declares to the Authorization Server S i its intention to communicate with the entity B; the Authorization Server S i determines an individual secret key K SiB which it shares with the entity B; c) the Authorization Server S i generates a session key K N,Si AB which is a one-way function of the individual secret key K SiB , and which is also a function of an integer N, referred to as the transaction number, allocated to the transaction; the Authorization Server S i sends the session key K N,Si AB to the entity A; d) the Authorization Server S i generates a filtering value IDTR N , which is a function dependent at least on the transaction number N in a non-invertible manner; the Authorization Server S i generates a transaction identifier IDTR N,Si , which is a function of the filtering value IDTR N , of the individual secret key K SiB , and of an identifier ID Si of the Authorization Server S i ; e) the Authorization Server S i supplies the entity B with elements comprising at least the transaction identifier IDTR N,Si ; f) using the transaction identifier IDTR N,Si , received during the step e), the entity B: identifies the current filtering value IDTR N within a set of filtering values pre-calculated by the entity B and associated with at least one predicted value of the transaction number, and obtains the Authorization Server identifier ID Si , and infers the corresponding individual secret key K SiB from the Authorization Server identifier ID Si ; and g) the entity B generates the session key K N,Si AB .