Algorithm 3. Device trust insertion and update rules for smart contract

Require: Trust Value ($T_v$), Node Identification ($node.id$), System Identification ($sys.id$), Fog Address ($fog\_address$) 1:Parameters: block_chain: Blockchain System: Object Gateway: Object Fog: Object 2:if (fog_system_mapping(sys.id) = fog_address) then 3: if (fog_verifier(fog_address,block_chain) = true) then 4:  if (Node_exist(node.id) = true) then 5:   if (system_node_mapping(sys.id) = node.id) then 6:    update_trust(node.ID, $T_v$, block_chain) 7:    node_trust_mapping(node.id, $T_v$) 8:   else 9:    return error() 10:   end if 11:  else 12:   return error() 13:  end if 14: else 15:  return error() 16: end if 17:else 18: return error() 19:end if