Patent ID: 7978851

Claim:
A stream encryption device for performing an encryption process in units of words by using a clock controller, the stream encryption device comprising: a first pseudo random number generator that generates a first pseudo random number sequence from key information; a second pseudo random number generator that generates a second pseudo random number sequence based on clock control performed in accordance with said first pseudo random number sequence; a keystream generator that generates a keystream by applying a nonlinear function calculation to said second pseudo random number sequence, wherein said keystream generator receives said second pseudo random number sequence as an input, applies thereto a nonlinear function calculation to generate a pre-keystream, performs exclusive OR operation over said pre-keystream and said first or second pseudo random number sequence, and performs a linear mixing process based on the result thereof to create a keystream; and an encrypter that generates an encrypted text by performing exclusive OR operation over said generated keystream and plain text.