Patent ID: 7433919

Claim:
A computer system comprising: a holding unit for holding pieces of data as processing objects and first characteristic values calculated based on the pieces of data while associating the pieces of data with the first characteristic values respectively; a providing unit for accepting a received characteristic value as an information request for a piece of data as a processing object from a requester and selecting the piece of data associated with the received characteristic value from the pieces of data held by the holding unit to provide the piece of data to the requester; an operation unit for calculating a characteristic value based on a piece of data as a processing object, wherein the operation unit divides the piece of data into a sequence of data fragments each having a predetermined size, calculates second characteristic values based on the data fragments respectively, holds the data fragments and the second characteristic values in the holding unit while associating the data fragments with the second characteristic values respectively, generates a sequence of the second characteristic values corresponding to the sequence of data fragments, calculates the characteristic value based on the sequence of the second characteristic values, and holds the sequence of the second characteristic values and the characteristic value in the holding unit while associating the sequence of the second characteristic values with the characteristic value.