Patent ID: 6584562
Filing Date: 2003-06-24
Classification: H04L,H04Q

Abstract:
A system for securing a telephone link between two subscriber sets, wherein the link is established through a switched telephone network or through a nonswitched telephone network at the request of the calling subscriber, the system comprising:two network terminals, wherein each of said network terminals comprises: an input/output port coupled to one of the subscriber sets; network encryption/decryption means; and a memory comprising an identifier of the port; two line terminals mutually linked both by the nonswitched telephone network and by the switched telephone network, and linked furthermore to the two network terminals by two subscriber lines; checking means connected to the switched and nonswitched telephone networks, configured to verify the identifiers of the two input/output ports, and configured to deliver an encryption authorization signal; means for generating encryption keys, wherein said means for generating encryption keys is coupled to the switched and nonswitched telephone networks and is configured: to generate at least one encryption key in response to the encryption authorization signal; to vary the encryption key temporally in a pseudo-random manner; and to forward the encryption key to the network encryption/decryption means and to the checking means; wherein the network encryption means is configured to encrypt, between the two network terminals and on the basis of the encryption key, information exchanged between the two subscriber sets, the information exchanged between the two subscriber sets being transmitted unenciphered between each network terminal and the corresponding subscriber set; wherein the switched telephone network is of the digital type, having (i) at least two bidirectional channels for exchanging information between the two subscriber sets and (ii) a service channel, wherein the checking means verifies the identifiers of the two input/output ports by using the service channel; and wherein the means for generating the encryption keys transmits the encryption key or keys over the service channel when the telephone link is established on the nonswitched network, or on the switched telephone network.