Patent ID: 8233627
Filing Date: 2012-07-31
Classification: G06Q,H04L

Abstract:
1. A key management system comprising: user terminals; and a key management apparatus connected to the user terminals, wherein each of the user terminals includes a first database to store a user private key specific to a user who uses the user terminal, and the key management apparatus includes a second database to store a user public key paired with the user private key stored in the first database and user information to indicate a user who uses a user terminal including the first database, by associating them with each other; a first encryption unit configured to encrypt an authority private key specific to a first authority given to at least one user among the users who use the user terminals, by using the user public key stored in the second database in association with user information to indicate a user given the first authority; a secret sharing unit configured to share in secret an authority private key specific to the first authority, into shared authority private keys; a second encryption unit configured to encrypt each of the shared authority private keys shared in secret, by using an authority public key specific to each of second authorities different from the first authority; and a third database which stores an authority private key encrypted by the first encryption unit and an authority public key paired with the authority private key, in association with the first authority, and stores shared authority private keys encrypted by the second encryption unit, in association with the second authorities.