Data encryption apparatus, data decryption apparatus, data encryption method, data decryption method, and data relay apparatus

A data decryption apparatus for decrypting, in a unit of a predetermined decryption data size, encrypted data transferred from a second apparatus to a first apparatus, comprising:

• a data decrypting unit that decrypts the encrypted data in the unit of the predetermined decryption data size, and upon remaining data below the predetermined decryption data size as a result of decryption, the data decrypting unit storing the remaining data in a storing unit and combining the remaining data in the storing unit with encrypted data subsequently sent from the second apparatus, so as to decrypt the combined data in units of the decryption data size;
• and
• a data sending unit that sends to the first apparatus the data decrypted by the data decrypting unit, wherein
• the encrypted data sent from the second apparatus contains data type information indicating a type of the data, and the data decrypting unit determines based on the data type information whether to decrypt the encrypted data, and decrypts the encrypted data upon determining to perform decryption.

A data encryption method for encrypting, in a unit of a predetermined encryption data size, data transferred from a first apparatus to a second apparatus, the data encryption method comprising:

• establishing, upon receiving from the second apparatus a first data transfer request indicating a first receivable size, a second receivable size being equal to or greater than the first receivable size and being a multiple of the predetermined encryption data size;
• sending to the first apparatus a second data transfer request indicating the second receivable size thus established;
• receiving data of the second receivable size from the first apparatus in response to the second data transfer request;
• encrypting, in the unit of the predetermined encryption data size, the data received from the first apparatus;
• sending the encrypted data to the second apparatus in units of the first receivable size;
• and
• upon remaining unsent data below the first receivable size after the sending the encrypted data sends the data, combining the unsent data with subsequent encryption data and sending the combined data to the second apparatus, the subsequent encryption data being encrypted by the encrypting subsequent to the remaining unsent data, wherein
• the data sent from the first apparatus contains data type information indicating a type of the data, and the data encrypting unit determines based on the data type information whether to encrypt the data, and encrypts the data upon determining to perform encryption.

A data decryption method for decrypting, in a unit of a predetermined decryption data size, encrypted data transferred from a second apparatus to a first apparatus, the data decryption method comprising:

• decrypting the encrypted data in the unit of the predetermined decryption data size;
• upon remaining data below the predetermined decryption data size as a result of decryption, storing the remaining data in a storing unit and combining the remaining data in the storing unit with encrypted data subsequently sent from the second apparatus, so as to decrypt the combined data in units of the decryption data size;
• and
• sending to the first apparatus the data decrypted by the decrypting, wherein
• the encrypted data sent from the second apparatus contains data type information indicating a type of the data, and the decrypting determines based on the data type information whether to decrypt the encrypted data, and decrypts the encrypted data upon determining to perform decryption.