An information recording medium manufacturing method includes the steps of: determining an encryption mode of each sector, which serves as an encrypt processing unit; generating encrypted data having different variations by using a plurality of cryptographic keys for a segment portion; generating encrypted data by using a single cryptographic key for a non-segment portion; and recording the encrypted data. In determining the encryption mode, a cryptographic key for each sector is specified on the basis of an auxiliary file including determination information indicating whether each sector is data of a segment portion or data of a non-segment portion and identification information for identifying a segment and a variation associated with the sector if the sector is found to be the data of a segment portion. In generating the encrypted data for the segment portion or for the non-segment portion, the encrypted data is generated by using the specified cryptographic key.