Keystream encryption device, method, and program

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 by the clock controller in accordance with the first pseudo random number sequence;
• a keystream generator that generates a keystream by receiving the second pseudo random number sequence as an input and by applying a nonlinear function calculation to the second pseudo random number sequence;
• and
• an encrypter that generates an encrypted text by performing exclusive OR operation over the generated keystream and plain text,
• wherein the clock controller controls the second pseudo random number generator based on clock control by using a root a of a polynomial which defines a finite field of degree 2, which is used to generate the second pseudo random number, and by multiplying α̂n in a bit shift operation of feedback polynomial or characteristic polynomial in a linear feedback shift register included in the second pseudo random number generator, where n represents a number of clocks determined by the clock controller.

A stream encryption method for performing an encryption process in units of words by using a clock controller, the method comprising:

• generating a first pseudo random number sequence from key information;
• generating a second pseudo random number sequence based on clock control performed by the clock controller according to the first pseudo random number sequence;
• generating a keystream by receiving the second pseudo random number sequence as an input and by applying thereto a nonlinear function calculation;
• and
• generating an encrypted text by performing exclusive OR operation over the generated keystream and plain text,
• wherein the clock control is performed by using a root α of a polynomial which defines a finite field of degree 2, which is used to generate the second pseudo random number, and by multiplying ân in a bit shift operation of feedback polynomial or characteristic polynomial in a linear feedback shift register included in the second pseudo random number generator, where n represents a number of clocks determined by the clock controller.

A computer-readable recording medium storing a stream encryption program, the stream encryption program causing a stream encryption device to perform an encryption process in units of words by using a clock controller, the encryption process comprising:

• generating a first pseudo random number sequence from key information;
• generating a second pseudo random number sequence based on clock control performed by the clock controller according to the first pseudo random number sequence, wherein the generating the second pseudo random number uses root a of a polynomial which defines a finite field of degree 2, which is used to generate the second pseudo random number, and multiplies α̂n in a bit shift operation of feedback polynomial or characteristic polynomial in a linear feedback shift register included in the second pseudo random number generator, where n represents a number of clocks determined by the clock controller;
• generating a keystream by receiving the second pseudo random number sequence as an input and by applying thereto a nonlinear function calculation;
• and
• generating an encrypted text by performing exclusive OR operation over the generated keystream and plain text.