Cryptographic device, cryptographic processing method, and cryptographic processing program

A cryptographic device that performs at least one of encryption and decryption according to a shared key encryption method, the device comprising:

• a first operation unit configured to receive a shared key and generate a plurality of expanded keys;
• and
• a second operation unit configured to receive plaintext or ciphertext and perform at least one of encryption and decryption that uses the plurality of expanded keys, wherein
• first data pieces are data pieces obtained by dividing the plaintext into predetermined units of words or data pieces obtained by dividing the ciphertext into predetermined units of words,
• the second operation unit includes
• a data array determination unit configured to determine, at a time of encryption, an array order of the first data pieces included in the plaintext as a first order, and determine, at a time of decryption, an array order of the first data pieces included in the ciphertext as a second order, and
• a main data computation unit configured to perform, on the first data pieces, computation of at least one of encryption and decryption in the determined order, and
• the second order is the reverse of the first order.