Information communication device and information communication program

An information communication device constituting an information communication system that is constructed through a peer-to-peer connection and uses a blockchain to operate groupware for managing group information shared among a plurality of members in a sharable state without a shared server, the information communication device being used individually by each member forming a group, the information communication device comprising:

• one or more processors;
• memory storing instructions, an operation unit, a transaction issuance unit, a transmission unit, a provisional reception unit, a transaction confirmation unit, and an update processing unit;
• a storage having a storage area for each member, the storage area storing the group information shared among the plurality of members;
• wherein the instructions that, when executed by the one or more processors, cause the one or more processors to perform operations comprising:
• processing, via the operation unit, addition, update, and/or deletion operations, on one group information of one storage area;
• detecting, via the transaction issuance unit, that the processing by the operation unit has been performed;
• issuing, via the transaction issuance unit, one transaction to the blockchain in response to the detecting, the one transaction indicating that the operation has been performed on the one group information;
• transmitting, via the transmission unit, the one group information after the operation to another member;
• receiving, via the provisional reception unit, another group information sent from the another member;
• accessing, via the transaction confirmation unit, based on that the provisional reception unit has provisionally received the another group information, the blockchain, wherein the accessing further comprises confirming presence or absence of another transaction indicating that the another member has performed an operation to change a content of another group information in another storage area from another information communication device used by the another member;
• and
• reflecting, via the update processing unit, based on that the presence of the another transaction newly issued has been confirmed, the another group information transmitted from the another information communication device, as legitimate information, in group information in the one storage area corresponding to the another group information.