Patent ID: 8638928
Filing Date: 2014-01-28
Classification: H04L

Abstract:
1. A key exchanging apparatus which receives a public key, a secret key, an identifier, a counterpart public key set, a counterpart identifier set, a session number, and a random number inputted thereto, performs communication with a plurality of counterpart apparatuses identified by identifiers belonging to the counterpart identifier set, and generates and outputs a public key, the apparatus comprising: a contribution random number generating unit that generates a contribution random number by using the random number; a contribution data generating unit that generates contribution data from the contribution random number generated by the contribution random number generating unit; a communication unit that transmits the contribution data to the plurality of counterpart apparatuses and receives contribution data from all of the counterpart apparatuses that participate in a key exchange with the key exchanging apparatus; a signing unit that generates a signer contribution confirmation signature with respect to a contribution data set including all the contribution data received by the communication unit from the plurality of counterpart apparatuses participating in the key exchange by using the secret key and the public key; a verifiable auxiliary data generating unit that generates auxiliary data and an auxiliary data validity certification sentence from the contribution data set and the contribution random number, the auxiliary data, the auxiliary data validity certification sentence and the contribution confirmation signature being transmitted to the plurality of counterpart apparatuses by the communication unit; a validity verifying unit that verifies validity of the auxiliary data by using the counterpart identifier set and the counterpart public key set, a contribution confirmation signature set, an auxiliary data set and an auxiliary data validity certification sentence set including data received by the communication unit from the plurality of counterpart apparatuses; and a key generating unit that generates the public key from the contribution data set and the auxiliary data received by the communication unit from the plurality of counterpart apparatuses.