tls_server_config :
  cert_file : "testdata/server.crt"
  key_file : "testdata/server.key"
  client_auth_type : "VerifyClientCertIfGiven"
  client_ca_file : "testdata/tls-ca-chain.pem"
  min_version: TLS13
  curve_preferences:
  - CurveP521