Patent ID: 8774415

Claim:
A key sharing device connected to a plurality of external devices through one or more paths, the plurality of external devices including a first device and a second device, the first device being directly connected to the key sharing device via a first path, the key sharing device comprising: a key storage unit configured to store cryptographic keys to be shared with the external devices; a determining unit configured to determine a second path for reaching the first device via the second device when a number of the cryptographic keys to be shared with the first device out of the cryptographic keys stored in the key storage unit is a predetermined threshold or smaller; a first generating unit configured to generate an initial key that is a new cryptographic key to be shared with the first device; an encrypting unit configured to encrypt the initial key by using the cryptographic key shared with the second device; and a first transmitting unit configured to transmit the encrypted initial key to the second device with addressing the first device as destination through the second path instead of the first path.