Patent ID: 7697684

Claim:
A data transformation apparatus having a key generating unit for generating output key data based on input key data K, and a data processing unit for performing at least one of encryption of data and decryption of data based on the output key data, the key generating unit comprising: a first G-bit key transformation unit for transforming G-bits key data, which is generated based on the input key data K, into first G-bit key data represented by G bits; and a second G-bit transformation unit for transforming the first G-bit key data inputted thereto into second G-bit key data represented by G bits, wherein the key generating unit generates the output key data differently when the input key data K is represented by G bits and 2G bits, respectively, such that; in response to receiving the input key data K represented by G bits, the key generating unit generates first G-bit key data K 1 by transforming the G-bits key data by the first G-bit key transformation unit, and outputs the first G-bit key data K 1 as the output key data, and in response to receiving the input key data K represented by the 2G bits, the key generating unit generates first G-bit key data K 1 by transforming one G-bits portion of the input key data K by the first G-bit key transformation unit, and generates second G-bit key data K 2 represented by G bits by transforming the first G-bit key data K 1 by the second G-bit transformation unit using the other G-bits portion of the input key data K, concatenates the first G-bit key data K 1 and the second G-bit key data K 2 , and outputs the concatenated key data as the output key data.