Patent ID: 11909867
Assignee: NIPPON TELEGRAPH AND TELEPHONE CORPORATION
Field: Digital communication (Electrical engineering)
Classification: CPC H | IPC H

Claim 0:
1. A key exchange system for generating a shared key for performing encrypted communication between a plurality of communication devices by an authenticated key exchange protocol using an ID based encryption, the key exchange system comprising:
the plurality of communication devices,
wherein each of the plurality of communication devices includes:
a memory, and
a processor configured to:
generate a short term private key by using a private key of a communication device,
generate a short term public key of the communication device using the short term private key and a pairing group G1 being one of asymmetric pairing groups G1 and G2 used for the ID based encryption, and
generate a shared key for performing encrypted communication with another communication device by performing a first pairing operation using the private key of the communication device and a short term public key generated in the other communication device, and performing a second pairing operation using the short term private key of the communication device and public information used in generating a private key of the other communication device,
wherein the private key of the communication device is generated using the pair group G2 being another one of the asymmetric pairing groups G1 and G2, and
wherein the processor is further configured to:
randomly select an element of a residue class Zq with q as a prime number to generate the short term private key using a predetermined function having, as an input, a string obtained by coupling string representing the selected element and the private key of the communication device;
generate the short term public key by computing the short term private key and the pairing group G1; and
generate the shared key by using a computation result of the first pairing operation, a computation result of the second pairing operation, a result of computing the short term private key and the short term public key generated in the other communication device, and a shared session ID between the communication device and the other communication device.