ssh-keygen -t rsa -b 4096 -f RS256.key passphraseはなし OpenSSH新形式の鍵を旧形式のPEMに変換 ssh-keygen -p -f RS256.key -m pem openssl rsa -in RS256.key -pubout -outform PEM -out RS256.key.pub JWTトークンの作成 https://jwt.io/