ARIA encryption/decryption apparatus and method, and method of generating initialization key for the same

An ARIA encryption/decryption method for encrypting and decrypting input data by repeating a plurality of rounds, the ARIA encryption/decryption method comprising:

• storing input data and a first round key in first and second registers, respectively;
• performing an exclusive OR operation on values stored in the first and second registers;
• substituting a result of the exclusive OR operation according to a predetermined control signal;
• storing a result of the substitution in the first register and storing a next round key in the second register if a current round is a final round;
• and
• performing an exclusive OR operation on values stored in the first and second registers to output a result of the ARIA encryption/decryption.

A method of generating initial keys for an ARIA encryption/decryption, the method comprising:

• storing a key generation key and a first key initialization constant in the first and second registers, respectively;
• performing a first exclusive OR operation on values stored in the first and second registers;
• substituting a result of the first exclusive OR operation;
• diffusing a result of the substitution;
• storing a result of the diffusion and initial keys calculated in a previous round in the first and second registers, respectively;
• performing a second exclusive OR operation for values stored in the first and second registers;
• storing a result of the second exclusive OR operation in the first and third registers and storing a next key initialization constant in the second register;
• repeating processes from the performing a first exclusive OR operation to the storing a next key initialization constant in the second register as many times as a number of key initialization constants;
• and
• outputting values stored in the third register as the initialization keys.