Patent ID: 8612399

Claim:
An alteration detecting apparatus comprising: an input unit that inputs a file; a storage unit that stores the file; an output unit that outputs the file; and an alteration detecting unit that produces first alteration detection data that is uniquely determined, from the file on the basis of an alteration detection data production process in response to an input of the file, stores the file and the first alteration detection data in the storage unit, produces second alteration detection data that is uniquely determined, from the file stored in the storage unit on the basis of the alteration detection data production process in response to an output request for the file, compares the first alteration detection data with the second alteration detection data and detects alteration of the file on the basis of the compared result, wherein the alteration detecting unit produces a first hash value as first alteration detection data from the file on the basis of a hash function, produces a second hash value as second alteration detection data from the file stored in the storage unit on the basis of the hash function, compares the first hash value with the second hash value, and detects alteration of the file on the basis of the compared result.