1. A cryptography-processing method for carrying out cryptography-processing computation based on hyperelliptic curve cryptography, said cryptography-processing method comprising: a base-point generation step of generating a divisor having a weight g 0 smaller than a genus g of a hyperelliptic curve to serve as a base point where 1≦g 0 <g; and a computation-processing step of carrying out scalar multiplication processing of divisors including said divisor serving as said base point.