KEY DISTRIBUTION SYSTEM AND METHOD, KEY GENERATION APPARATUS, REPRESENTATIVE USER TERMINAL, SERVER APPARATUS, USER TERMINAL, AND PROGRAM

• US 20200136813A1
• Filed: 04/27/2018
• Published: 04/30/2020
• Est. Priority Date: 05/09/2017
• Status: Active Grant

• Current Assignee: Nippon Telegraph and Telephone Corporation
• Original Assignee: Nippon Telegraph and Telephone Corporation
• Inventors: YOSHIDA, Reo, KOBAYASHI, Tetsutaro, KAWAHARA, Yuto, FUJI, Hitoshi, YONEYAMA, Kazuki
• Granted Patent: US 11,336,436 B2
• Time in Patent Office: Days
• CPC Class Codes: H04L 63/062 for key distribution, e.g. centrally by trusted party cryptographic mechanisms or cryptographic arrangements for key distribution involving a central third party H04L9/0819
• CPC Class Codes: H04L 63/065 for group communications cryptographic mechanisms or cryptographic arrangements for key management involving conference or group key H04L9/0833
• CPC Class Codes: H04L 9/0825 using asymmetric-key encryption or public key infrastructure [PKI], e.g. key signature or public key certificates
• CPC Class Codes: H04L 9/083 involving central third party, e.g. key distribution center [KDC] or trusted third party [TTP]
• CPC Class Codes: H04L 9/0861 Generation of secret information including derivation or calculation of cryptographic keys or passwords
• CPC Class Codes: H04L 9/3073 involving pairings, e.g. identity based encryption [IBE], bilinear mappings or bilinear pairings, e.g. Weil or Tate pairing

Abstract

A key distribution system includes a representative user terminal 2_p, a server apparatus 3, and an (n+1)-th user terminal 2_n+1. The representative user terminal 2_p uses a public key for the (n+1)-th user terminal 2_n+1 and information for identifying the (n+1)-th user terminal 2_n+1 to encrypt key information with a predetermined encryption function in Certificate-less Encryption to obtain ciphertext. The server apparatus 3 sends the ciphertext to the (n+1)-th user terminal 2_n+1 when the (n+1)-th user terminal 2_n+1 is added. The (n+1)-th user terminal 2_n+1 uses a complete secret key for the (n+1)-th user terminal 2_n+1 and the information for identifying the (n+1)-th user terminal 2_n+1 to decrypt the ciphertext with a predetermined decryption function to obtain the key information.

Claims

1. A key distribution system comprising:

a representative user terminal;

a server apparatus; and

an (n+1)-th user terminal;

the representative user terminal using a public key for the (n+1)-th user terminal and information for identifying the (n+1)-th user terminal in Certificate-less Encryption to encrypt key information with a predetermined encryption function in Certificate-less Encryption to obtain ciphertext, and sending the obtained ciphertext to the server apparatus;

the server apparatus sending the ciphertext to the (n+1)-th user terminal when the (n+1)-th user terminal is added; and

the (n+1)-th user terminal using a complete secret key for the (n+1)-th user terminal and the information for identifying the (n+1)-th user terminal in Certificate-less Encryption to decrypt the ciphertext with a predetermined decryption function in Certificate-less Encryption to obtain the key information.

2. The representative user terminal in the key distribution system according to claim 1.

3. The server apparatus in the key distribution system according to claim 1.

4. A user terminal serving as the (n+1)-th user terminal in the key distribution system according to claim 1.

6. A program for making a computer function as one of the representative user terminal according to claim 2, the server apparatus according to claim 3, and the user terminal according to claim 4.

5. A key distribution method comprising:

a step in which a representative user terminal uses a public key for an (n+1)-th user terminal and information for identifying the (n+1)-th user terminal in Certificate-less Encryption to encrypt key information with a predetermined encryption function in Certificate-less Encryption to obtain ciphertext and sends the obtained ciphertext to a server apparatus;

a step in which the server apparatus sends the ciphertext to the (n+1)-th user terminal when the (n+1)-th user terminal is added; and

a step in which the (n+1)-th user terminal uses a complete secret key for the (n+1)-th user terminal and the information for identifying the (n+1)-th user terminal in Certificate-less Encryption to decrypt the ciphertext with a predetermined decryption function in Certificate-less Encryption to obtain the key information.