An electronic contract system used to make a contract concerning predetermined contractual terms between a first transacting party and a second transacting party through a network, the electronic contract system comprising a first information processor used by the first transacting party and a second information processor used by the second transacting party,
- the first information processor including:
- a first contractual terms storing unit for storing contractual terms data C showing a character string of the contractual terms;
- a first identification data generating unit having an operational function based on a predetermined algorithm that obtains output data univocally fixed with respect to input data, so as to generate first contractual terms identifying data ID1 univocally fixed with respect to the contractual terms data C by performing an arithmetical operation based on the algorithm with respect to the contractual terms data C;
- and
- a contractual terms information transmitting unit for transmitting contractual terms information including the contractual terms data C to the second information processor through the network;
- the second information processor including:
- a second contractual terms storing unit for storing the contractual terms data C in the contractual terms information that has been transmitted;
- a second identification data generating unit for generating second contractual terms identifying data ID2 univocally fixed with respect to the contractual terms data C stored in the second contractual terms storing unit by performing an arithmetical operation based on the algorithm with respect to the~contractual terms data C stored in the second contractual terms storing unit;
- a second transacting-party signature generating unit for generating a digital signature Sig2 of the second transacting party with respect to the second contractual terms identifying data ID2;
- and
- a formal contractual proposal information transmitting unit for transmitting formal contractual proposal information including the second contractual terms identifying data ID2 and the digital signature Sig2 of the second transacting party to the first information processor through the network;
- wherein the first information processor further includes:
- a first signature verifying unit for verifying consistency between the second contractual terms identifying data ID2 and the digital signature Sig2 of the second transacting party in the formal contractual proposal information that has been transmitted;
- a first identification data verifying unit for verifying a coincidence between the first contractual terms identifying data ID1 and the second contractual terms identifying data ID2;
- a first transacting-party signature generating unit for generating a digital signature Sig1 of the first transacting party with respect to contractual terms identifying data ID that has coincided through verification of the first identification data verifying unit;
- and
- a formal contractual acceptance information transmitting unit for transmitting formal contractual acceptance information including the coinciding contractual terms identifying data ID and the digital signature Sig1 of the first transacting party to the second information processor through the network;
- and
- the second information processor further includes:
- a second signature verifying unit for verifying consistency between the coinciding contractual terms identifying data ID and the digital signature Sig1 of the first transacting party in the formal contractual acceptance information that has been transmitted;
- and
- a second identification data verifying unit for verifying a coincidence between the second contractual terms identifying data ID2 generated by the second identification data generating unit and the coinciding contractual terms identifying data ID.