The purpose of FAC is to let other nodes synchronize since node A has made the deletion. In our scheme, there will be at least one node acting as a master node in order to upload the correct FAC for other nodes to perform comparison. In the example below, node A will be the master node. Ethereum smart contract will verify the address via msg.sender to check if the node is validfor uploading correct FAC. After the validation, smart contract will keep the record of the uploader’s address,the correct FAC and the timestamp in FAC table as shown in Table I. The table consists of timestamps, the address of uploader, the FAC and the status of each node. First,node A triggers the deletion, and then the status of node A will be updated to the latest. Node B and C will need to perform removing unpin file procedure. In addition, the setting of performing garbage collection procedure in other nodes is in every 5 seconds, which is adjustable. Next, node B and C need to generate a FAC of their own current IPFS directory and compare with the latest FAC. In the end, the smart contract will record the comparison result. As long as the result is the same, the filed will set to be True. If they are not the same, the smart contract will trigger an event to log the difference of a specific node.