The present invention allows a device to easily generate pseudorandom numbers using information about a living body. An imaging element outputs an image signal equivalent to imaging light reflecting a target of identification inside a certain part of a living body. The device extracts data from the image signal output from the imaging element. This data reflects a change arising from the living body and a change of the imaging element. The device then generates a pseudorandom number using the data as a seed. Specifically, to produce the seed, the device sequentially selects two image signals output from the imaging element as a pair, sequentially detects difference between the pair of image signals, recognizes one of the detected differences as criterion, and then calculates a degree of difference between the criterion and the rest of differences.