Method and device for generating big prime number

The present invention is suitable for the technical field of information security and provides a method and a device for generating a big prime number. The method comprises the following steps: generating a big odd number at random; carrying out trial division on the big odd number by a first small prime number to obtain preliminarily screened data; after the end of the first trial division by the small prime number, continuing to execute trial division on other big odd numbers; meanwhile, calling a modular exponentialtion unit of RSA (Rivest Shamir Adlemen) hardware for executing at least once modular exponentialtion on the preliminarily screened data till the big prime number is obtained. According to the present invention, the first trial division by the small prime number is completed independently; then the modular exponentialtion and the trial division by the small prime number are concurrently carried out; the steps are repeated till the final prime number judging passes; and the generation time of the big prime number is close to the calculation time of modular exponentialtion hardware without individually spending the time on the trial division by the small prime number, thereby reducing the overall generation time of the big prime number and increasing the production efficiency of the big prime number.