The present invention is related to a method for allocating keys used in encrypted communications to both a communication source terminal and a communication destination terminal, and also related to a key allocation system.
In the case that both a communication source apparatus and a communication destination apparatus (will be simply referred to as “terminals” hereinafter) perform an encrypted communication via a network, data of the communication is encrypted and then the encrypted data is transmitted/received. While both the communication source terminal and the communication destination terminal have previously and commonly owned both setting information and keys which are used in an encrypted communication between the communication source terminal and the communication destination terminal, the communication source terminal is encryption-communicated with the communication destination terminal by employing the setting information and the keys, which are commonly owned.
For instance, in a case that a key is shared by employing public key encryption, the below-mentioned encrypted communication will be carried out.
That is, a communication source terminal acquires a public key of a communication destination terminal, produces a key which is used so as to perform an encrypted communication with the communication destination terminal, and encrypts this key used for the encrypted communication by employing this public key, and then, transmits the encrypted key to the communication destination terminal. Also, the communication destination terminal receives the key used for the encrypted communication, which has been encrypted by this public key of the communication destination terminal, and then, decrypts the received encrypted key based upon a private key of the communication destination terminal.
In the above-explained method, in order that the communication source terminal executes encrypted communications with respect to plural communication destination terminals, this communication source terminal and the respective communication destination terminals must commonly own the setting information and the keys used for the encrypted communications. Therefore, there is such a problem that loads of the communication source terminal are increased.
As a consequence, the below-mentioned encrypted communication technique has been proposed. That is, while a server apparatus (will be referred to as “server” hereinafter) which allocates both the setting information and the key for the encrypted communication to both a communication source terminal and a communication destination terminal is installed on a network, both the communication source terminal and the communication destination terminal execute an encrypted communication by employing the above-described setting information and keys for the encrypted communication. Mark Baugher et. al., “MSEC Group Key Management Architecture <draft-ietf-msec-gkmarch-07.txt>”, Jan. 30, 2003, IETF (Internet Engineering Task Force) pages 3 to 13, refer to: <URL: http://www.ietf.org/internet-drafts/draft-ietf-msec-gkmarch-07.txt>.
Also, in order that a validity of a communication counter party is confirmed in a communicating operation established via a network, the communication counter party must be authenticated before the communicating operation is carried out. As one of methods for authenticating communication counter parties, such an authenticating method with employment of an electronic signature is provided. Concretely speaking, both a communication source terminal and a communication destination terminal, which are communicated to each other, exchange IDs and public key s, to which electronic signatures have been applied. Then, both the communication source terminal and the communication destination terminal verify both the received electronic signatures and the received public key s so as to authenticate the communication counter parties with each other.