Key distribution system and method, key generation device, representative user terminal, server device, user terminal, and program

摘要

The key generation system obtains a ciphertext by encrypting key information using a public key of the (n + 1) th user terminal 2n + 1 and information for identifying the (n + 1) th user terminal 2n + 1 by a predetermined encryption function of Certificate less Encryption. Identify the representative user terminal 2p, the server device 3 that transmits a ciphertext to the (n + 1) th user terminal 2n + 1 when adding the (n + 1) th user terminal 2n + 1, and the entire secret key of the (n + 1) th user terminal 2n + 1 and the (n + 1) th user terminal 2n + 1. And an (n + 1) th user terminal 2n + 1 that obtains key information by decrypting the ciphertext with a predetermined decryption function using the information for the user.