Methods and apparatus of key pairing for D2D devices under different D2D areas

1. An apparatus comprising:

at least one processor; and

at least one memory including computer program code,

the at least one memory and the computer program code configured to, with the at least one processor, cause the apparatus to at least:

receive, at a first radio access network node serving a first device-to-device area and from a first user equipment in the first device-to-device area, a request for keys for a device-to-device communication between the first user equipment and a second user equipment, wherein the request comprises an identification of a second device-to-device area where the second user equipment is located, the second device-to-device area being different from the first device-to-device area, the apparatus comprising or comprised in the first radio access network node;

identify a second radio access network node serving the second device-to-device area based on the identification;

send, to the second radio access network node, a request for a security context of the second user equipment;

receive, from the second radio access network node, the security context for obtaining the keys for the device-to-device communication; and

derive, based on the received security context of the second user equipment, the keys for the device-to-device communication.

2. An apparatus of claim 1 , wherein the security context of the second user equipment comprises a user apparatus-specific key which is shared between the second user equipment and the second radio access network node.

3. An apparatus of claim 1 , wherein the apparatus is further caused to at least:

send the keys for the device-to-device communication to the first user equipment, and wherein the first radio access network node comprises a base station.

4. An apparatus of claim 1 , wherein the first radio access network node is an enhanced Node B coupled to, or including, a device-to-device registration server function server, and/or the second radio access network node is an enhanced Node B coupled to, or including, a device-to-device registration server function server.

5. An apparatus comprising:

at least one processor; and

at least one memory including computer program code,

the at least one memory and the computer program code configured to, with the at least one processor, cause the apparatus to at least:

receive, at a first user equipment, a notification of device-to-device services from a second user equipment, wherein the notification comprises an identification of a second device-to-device area where the second user equipment is located, and the first user equipment is in a first device-to-device area different from the second device-to-device area, the apparatus comprising or comprised in the first user equipment;

send, to a first radio access network node serving the first device-to-device area, a request for keys for a device-to-device communication between the first user equipment and the second user equipment, wherein the request comprises the received identification so that a security context of the second user equipment is available for the first radio access network node from a second radio access network node serving the second device-to-device area; and

in response to the request, receive the keys for the device-to-device communication which are derived by the first radio access network node based on the security context.

6. An apparatus of claim 5 , wherein the security context of the second user equipment comprises a user apparatus-specific key which is shared between the second user equipment and the second radio access network node.

7. An apparatus of claim 5 , wherein the apparatus is further caused to at least broadcast a notification of device-to-device services, wherein the notification indicates an identification of a device-to-device area where the first user equipment is located.

8. An apparatus comprising:

at least one processor; and

at least one memory including computer program code,

the at least one memory and the computer program code configured to, with the at least one processor, cause the apparatus to at least:

receive, at a first radio access network node and from a user equipment, a message indicating that the user equipment is going to move from a first device-to-device area served by the first radio access network node to a second device-to-device area served by a second radio access network node, the apparatus comprising or comprised in the first radio access network node; and

in response to the message, forward a security context for device-to-device services of the user equipment to the second radio access network node.

9. An apparatus of claim 8 , wherein the apparatus is further caused to at least:

receive, from the second radio access network node, an indication of releasing the security context for device-to-device services of the user equipment; and

remove the security context in response to the indication.

10. An apparatus of claim 8 , wherein the message comprises an identification of the second device-to-device area.

11. An apparatus of claim 8 , wherein the security context for device-to-device services of the user equipment comprises a user apparatus-specific key of the user equipment which is shared between the user equipment and the first radio access network node.

12. An apparatus of claim 11 , wherein the apparatus is further caused to at least:

receive a relocated identification of the user equipment from a core network node; and

update the security context by associating the relocated identification with the user apparatus-specific key.