Method and devices for secure communications in a telecommunications network

An Authorization Server configured to provide secure communications in a telecommunications network during a transaction between an entity A and an entity B, the Authorization Server programmed to:

• identify and authenticate an entity A holding an identifier IDA,
• determine an individual secret key KSiB which the Authorization Server Si (where i=1, 2, . . . , p, and p is a strictly positive integer) shares with an entity B with which the entity A declares its intention to communicate,
• generate a session key KN,SiAB and send it to the entity A, the session key KN,SiAB being a one-way function of the individual secret key KSiB and being a function of an integer N, referred to as the transaction number, allocated to the transaction,
• generate a filtering value IDTRN, which is a function dependent at least on the transaction number N in a non-invertible manner,
• generate a transaction identifier IDTRN,Si, which is a function of the filtering value IDTRN, of the individual secret key KSiB, and of an identifier IDSi of the Authorization Server Si, and
• supply the entity B with elements comprising at least the transaction identifier IDTRN,Si.

A device, referred to as entity B, configured to provide secure communications in a telecommunications network, wherein, during a transaction involving the entity B and an entity A, the entity B is configured to:

• receive elements comprising at least a transaction identifier IDTRN,Si generated by an Authorization Server Si (where i=1, 2, . . . , p, and p is a strictly positive integer), wherein the transaction identifier IDTRN,Si is a function of a filtering value IDTRN, an individual secret key KSiB shared by the entity B and the Authorization Server Si, and an identifier IDSi of the Authorization Server Si, and wherein the filtering value IDTRN is a function dependent at least, in a non-invertible manner, on an integer N, referred to as the transaction number, allocated to the transaction,
• with the aid of said use the transaction identifier IDTRN,Si to:
• identify the current filtering value IDTRN 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
• obtain the Authorization Server identifier IDSi, and infer the corresponding individual secret key KSiB from the Authorization Server identifier IDSi;
• and
• generate a session key KN,SiAB which is a function of the transaction number N and a one-way function of the individual secret key KSiB.

A device, referred to as entity A, configured to provide secure communications in a telecommunications network, wherein, during a transaction involving the entity A and an entity B, the entity A is configured to:

• identify itself and authenticate itself as the holder of an identifier IDA by communicating with an Authorization Server Si (where i=1, 2, . . . , p, and p is a strictly positive integer),
• declare to the Authorization Server Si its intention to communicate with an entity B,
• receive a session key KN,SiAB from the Authorization Server Si, wherein the session key KN,SiAB is a one-way function of an individual secret key KSiB shared by the Authorization Server Si and the entity B is a function of an integer N, referred to as the transaction number, allocated to the transaction,
• receive a transaction identifier IDTRN,Si from the Authorization Server Si, wherein the transaction identifier IDTRN,Si is a function of a filtering value IDTRN, the individual secret key KSiB, and an identifier IDSi of the Authorization Server Si, and wherein the filtering value IDTRN is a function dependent at least, in a non-invertible manner, on the transaction number N, and
• send elements comprising at least the transaction identifier IDTRN,Si to the entity B.