Device for securing a telephone link between two subscriber sets

A method for securely communicating data from a first subscriber set to a second subscriber set, the method comprising:

• establishing a link through a switched telephone network or through a nonswitched telephone network at the request of the calling subscriber;
• the first subscriber set providing unencrypted data to a first network terminal associated with the first subscriber set;
• verifying the identity of the first network terminal and the identity of a second network terminal associated with the second subscriber set;
• in response to positive verification of the identities of the first and second network terminals, (i) encrypting the unencrypted data, (ii) the first network terminal communicating the encrypted data to the second network terminal, and (iii) unencrypting the encrypted data;
• the second network terminal providing the unencrypted data to a second subscriber set;
• wherein said encrypting the data includes generating one or more encryption/decryption keys and providing the encryption/decryption keys to the second network terminal through a service channel of a switched telephone network;
• and
• wherein said verifying the identities of the first and second network terminals is performed by a checking system that communicates with the first and second network terminals through a service channel of a switched telephone network.

A system for securing a telephone link between a first telephone unit and a second telephone unit, wherein the link is established through a switched telephone network or through a nonswitched telephone network at the request of a calling subscriber, the system comprising:

• a first network terminal and a second network terminal, wherein each of said network terminals comprises:
• an input/output port coupled to one of the telephone units;
• encryption/decryption circuit coupled to said input/output port;
• and
• a memory coupled to said input/output port and holding an identifier of said input/output port;
• a first line terminal and a second line terminal mutually linked both by the nonswitched telephone network and by the switched telephone network, wherein each of said line terminals is linked by a subscriber line to a corresponding one of said two network terminals;
• an identity verification system 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;
• a key server, wherein said key server is coupled to the switched and nonswitched telephone networks and is configured to generate least one encryption key in response to the encryption authorization signal, to update the encryption key temporally in a pseudo-random manner, and to forward the encryption key to the encryption/decryption circuit and to the identity verification system;
• wherein the encryption/decryption circuit is configured to encrypt, between the two network terminals and on the basis of the encryption key, information exchanged between the two telephone units, the information exchanged between the two telephone units being transmitted unenciphered between each network terminal and the corresponding telephone unit;
• wherein the telephone link is established on the switched telephone network, and wherein the telephone link is a digital link comprising at least two bidirectional channels for exchanging information between the two telephone units, and a service channel, and wherein the key server transmits the encryption key or keys over the service channel;
• wherein the switched telephone network is of the digital type with at least two bidirectional channels for exchanging information between the two telephone units, and a service channel, wherein the identity. verification system verifies the identifiers of the two input/output ports by using the service channel;
• and
• wherein the encryption/decryption circuit transmits the encryption key or keys over the service channel when the telephone link is established on the nonswitched network.