An information processing system, comprising an information processing apparatus, a data storage unit attachable to the information processing apparatus, a content usage managing server, and a content correspondence information providing server, wherein the information processing apparatus comprises a data processing unit configured to: access the data storage unit (20, 120) attached to the information processing apparatus, receive a block identifier from the content usage managing server, the block identifier being information for designating a block for storing an encryption key, wherein the data storage unit comprises a protected area including a block allowing access thereto based on an access right check made on each block and an in-storage data processing unit configured to: store encrypted content and data containing the encryption key to be used in decrypting the encrypted content, make an access right check to determine whether the content correspondence information providing server is a server allowed to write data into the block corresponding to the block identifier based on a server certificate set for the content correspondence information providing server, and allow the content correspondence information providing server to write the encryption key into the block in the protected area when an access right is confirmed, wherein the content usage managing server is configured to: determine a block for storing the encryption key to be used in decrypting the encrypted content, and notify the content correspondence information providing server of the block identifier, and wherein the content correspondence information providing server is configured to perform a process to write the encryption key into a block corresponding to the block identifier transmitted from the content usage managing server. access the data storage unit (20, 120) attached to the information processing apparatus, receive a block identifier from the content usage managing server, the block identifier being information for designating a block for storing an encryption key, wherein the data storage unit comprises a protected area including a block allowing access thereto based on an access right check made on each block and an in-storage data processing unit configured to: store encrypted content and data containing the encryption key to be used in decrypting the encrypted content, make an access right check to determine whether the content correspondence information providing server is a server allowed to write data into the block corresponding to the block identifier based on a server certificate set for the content correspondence information providing server, and allow the content correspondence information providing server to write the encryption key into the block in the protected area when an access right is confirmed, store encrypted content and data containing the encryption key to be used in decrypting the encrypted content, make an access right check to determine whether the content correspondence information providing server is a server allowed to write data into the block corresponding to the block identifier based on a server certificate set for the content correspondence information providing server, and allow the content correspondence information providing server to write the encryption key into the block in the protected area when an access right is confirmed, determine a block for storing the encryption key to be used in decrypting the encrypted content, and notify the content correspondence information providing server of the block identifier, and