A variety of cryptographic algorithms are used throughout many social infrastructures. On the other hand, with the spectacular development of quantum computers in recent years, it has become known that when the processing performance of quantum computers reaches a certain level, some crypto algorithms will be able to decrypted in a realistic time. Therefore, it is said that it is necessary to shift the currently used crypto algorithms to crypto algorithms that are safe against attacks by even quantum computers. In this presentation, we will discuss points to keep in mind for implementing such countermeasure while maintaining cost-effectiveness.