Method and device for generating pseudorandom number, and method and device for encryption using pseudorandom number

An apparatus for generating a pseudo-random number having a desired data amount that is used for encrypting digital data, said apparatus comprising:

• a memory device which stores a pseudo-random number as a seed;
• and
• a processor unit configured to divide the seed stored in the memory device into a predetermined number of blocks, calculate exclusive-ORs on combinations of blocks being different from one another of the predetermined number of blocks, respectively, to create a plurality of blocks of new pseudo-random numbers, and merge a plurality of blocks of the new pseudo-random numbers to generate a new pseudo-random number having a greater data amount as compared with the seed,
• wherein the processor unit further configured to compare a data amount of the new pseudo-random number as generated with a desired data amount, and if the comparison result is less than the desired data amount, the seed stored in the memory device is replaced by the new pseudo-random number as generated, which is stored as a new seed in the memory device, and said dividing, creating, generating and comparing processes are repeated until a pseudo-random number having the desired amount is obtained.

An encrypting system including:

• a pseudo-random number generating apparatus which generates a pseudo-random number based on a seed;
• and
• an encrypting apparatus which encrypts data including a message, a voice, an image or a moving image, for each predetermined amount of data, based on the pseudo-random number generated by the pseudo-random number generating apparatus,
• wherein the pseudo-random number generating apparatus comprises a memory device which stores a pseudo-random number as a seed, and a processor unit configured to divide the seed stored in the memory device into a predetermined number of blocks, calculate exclusive-ORs on combinations of blocks being different from one another of the predetermined number of blocks, respectively, to create a plurality of blocks of new pseudo-random numbers, and merge a plurality of blocks of the new pseudo-random numbers to generate a new pseudo-random number having a greater data amount as compared with the seed, and
• wherein said pseudo-random number generating apparatus further generates a pseudo-random number to be used for the succeeding encryption by using as a seed a predetermined amount of random number of the pseudo-random number used for the immediately preceding encryption of the predetermined amount of data.

An encrypting method including:

• storing a pseudo-random number as a seed in a memory device;
• dividing the seed stored in the memory device into a predetermined number of blocks;
• creating a plurality of blocks of new pseudo-random numbers by calculating exclusive-ORs on combination of blocks being different from one another of the predetermined number of blocks, respectively, using a processor unit;
• generating a new pseudo-random number having a greater data amount as compared with the seed by merging the plurality of blocks of new pseudo-random numbers;
• and
• encrypting data including a message, a voice, an image or a moving image, for each predetermined amount of data, based on a pseudo-random number obtained from the generated new pseudo-random number,
• wherein a pseudo-random number to be used for the succeeding encryption is generated by using as a new seed a predetermined amount of random number of the pseudo-random number used for the immediately preceding encryption of the predetermined amount of data.