Patent ID: 8005219

Claim:
A data decryption apparatus that decrypts encrypted data, comprising: a first data-receiving unit that receives, each time an encryption specification is changed, a first data set, in which information on the changed encryption specification is embedded, through a first communication path; a time-information obtaining unit that obtains first time information corresponding to the reception time of each first data set by the first data receiving unit; a time-information storage unit that stores each first time information obtained by the time-information obtaining unit with each first data set; a second data-receiving unit that receives a second data set through a second communication path, the second data set being encrypted based on an encryption specification and appended by second time information corresponding to the performing of data encryption on the second data set; and an encryption-specification selecting unit that selects an encryption specification for use in decryption of the second data set from a plurality of encryption specifications based on first time information stored in the time-information storage unit and the second time information appended to the second data set received by the second data-receiving unit.