A content transaction management server device includes: a memory storing decryption keys used in decryption of encrypted content data; a communication unit for information; a payment-request reception unit receiving, through the communication unit, a first storage address indicating a storage area where the decryption keys of encrypted content data in the memory are stored and user identifiers identifying users who are purchasers of the encrypted content data; a payment-procedure processing unit implementing payment-procedure processes related to purchase transactions of encrypted content data by a user identified by user identifiers in the payment request; and a decryption-key transmission unit that, after payment-procedure processing based on the payment-procedure processing unit is completed, reads out, from the memory, decryption keys stored in the storage area indicated by the first storage address included in the payment request and transmits, through the communication unit, the decryption keys to the transmission source of the payment request.