Patent ID: 8577038

Claim:
A method for generating a pseudo-random number having a desired data amount that is used for encrypting digital data, said method comprising: 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 combinations 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 a plurality of blocks of the new pseudo-random numbers; and comparing a data amount of the new pseudo-random number as generated with a desired data amount, wherein 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 are repeated until a pseudo-random number having the desired amount is obtained.