Patent attributes
A storage unit stores a size of a free area of storage of target equipment, and software saved in the storage. The generation unit generates a graph including a number of nodes according to the size of the free area of the storage, and transmits the graph to the target equipment. The calculation unit calculates a hash value corresponding to each software block saved in the storage. The verification unit verifies the presence or absence of tampering of the storage of the target equipment using the hash value corresponding to the block calculated, a response calculated using the graph returned to a challenge that specifies a node of the graph, and a hash value corresponding to the block returned as the response to the challenge that specifies the block.