Expansion key generating device, encryption device and encryption system

An encryption device that encrypts plain text data using encryption key data comprising:

• an expansion key generating device operable to receive encryption key data as input, and output plural expansion key data;
• and
• a unit operable to encrypt the plain text based on the plural expansion key data generated from the expansion key generating device, and generate ciphertext data;
• wherein the expansion key generating device includes:
• a data dividing unit operable to divide the encryption key data into plural part key data;
• and
• plural key conversion units, which are connected in series, operable to receive the plural part key data as input, and output the plural expansion key data,
• each of the plural key conversion units includes:
• an output calculation unit operable to receive the plural part key data or plural output data from a preceding key conversion unit as plural input data, execute a fixed conversion process to each of the plural input data in a way each bit value of each of the plural input data does not interfere each other, and output plural output data into a subsequent key conversion unit;
• and
• an expansion key calculation unit operable to combine the plural input data, and generate the expansion key data.

A decryption device that decrypts ciphertext data using encryption key data comprising:

• an expansion key inverse generating unit operable to receive the encryption key data, and generate plural expansion key data in a reverse order of an expansion key generating device;
• and
• a data inverse scrambling unit operable to decrypt the ciphertext data based on the plural expansion key data,
• wherein the expansion key inverse generating device includes:
• a data dividing unit operable to divide the encryption key data into plural part key data;
• and
• plural key conversion units, which are connected in series, operable to receive the plural part key data as input, and output the plural expansion key data,
• each of the plural key conversion units includes:
• an output calculation unit operable to receive the plural part key data or plural output data from a preceding key conversion unit as plural input data, execute a fixed conversion process to each of the plural input data in a way each bit value of each of the plural input data does not interfere each other, and output plural output data to a subsequent key conversion unit;
• and
• an expansion key calculation unit operable to combine the plural input data, and generate the expansion key data, and
• the expansion key inverse generating unit includes:
• a key modification unit operable to execute specific stages of processing in the key conversion units in the expansion key generating device by a stage of processing;
• and
• plural key inverse conversion units that are connected in series, and
• wherein each of the plural key inverse conversion units respectively receives output data from the key modification unit or output data from a preceding key inverse conversion unit as input data, generates the expansion key data and output data to a subsequent key inverse conversion unit from the input data, and the generated expansion key data is generated in a reverse order of the expansion key generating device.

An encryption system comprising:

• an encryption device that encrypts plain text data using encryption key data, and generates ciphertext data;
• and
• a decryption device that decrypts the ciphertext data using the encryption key data,
• wherein the encryption device includes:
• an expansion key generating unit operable to receive the encryption key data as input, and output plural expansion key data;
• and
• a data scrambling unit operable to encrypt the plain text data based on the plural expansion key data,
• the expansion key generating unit includes:
• a data dividing unit operable to divide the encryption key data into plural part key data;
• and
• plural key conversion units, which are connected in series, operable to receive the plural part key data as input, and output the plural expansion key data, and
• each of the plural key conversion units includes:
• an output calculation unit operable to receive the plural part key data or the plural output data from a preceding key conversion unit as plural input data, execute a fixed conversion process to each of the plural input data in a way each bit value of each of the plural input data does not interfere each other, and output plural output data to a subsequent key conversion unit;
• and
• an expansion key calculation unit operable to combine the plural input data, and generate the expansion key data.

An expansion key generating method for receiving encryption key data as input and outputting plural expansion key data, including:

• a step for dividing the encryption key data into plural part key data;
• and
• plural key conversion steps for receiving the plural part key data as input and outputting the plural expansion key data,
• wherein each of the plural key conversion steps includes:
• a step for receiving the plural part key data or the plural output data output in a preceding key conversion step as plural input data, executing a fixed conversion process to each of the plural input data in a way each bit value of each of the plural input data does not interfere each other, and outputting plural output data used in a subsequent key conversion step;
• and
• a step for combining the plural input data, and generating the expansion key data.

A program having a computer function as an encryption device that executes an encryption process to plain text data using encryption key data,

• wherein the encryption device includes:
• an expansion key generating unit operable to receive the encryption key data as input, and output plural expansion key data;
• and
• a unit operable to encrypt the plain text data based on the plural expansion key data, and generate ciphertext data,
• the expansion key generating unit includes:
• a data dividing unit operable to divide the encryption key data into plural part key data;
• and
• plural key conversion units, which are connected in series, operable to receive the plural part key data as input, and output the plural expansion key data, and
• each of the plural key conversion units includes:
• an output calculation unit operable to receive the plural part key data or plural output data from a preceding key conversion unit as plural input data, execute a fixed conversion process to each of the plural input data in a way each bit value of each of the plural input data does not interfere each other, and output plural output data to a subsequent key conversion unit;
• and
• an expansion key calculation unit operable to combine the plural input data, and generate the expansion key data.