es256のpemを生成する

Pairで作る

openssl ecparam -genkey -name prime256v1 -noout -out ec256-key-pair.pem

https://notes.salrahman.com/generate-es256-es384-es512-private-keys/

別々で作る

bash
openssl ecparam -genkey -name prime256v1 -noout -out ec_private.pem
openssl ec -in ec_private.pem -pubout -out ec_public.pem

https://cloud.google.com/iot/docs/how-tos/credentials/keys