OptionalcurveEC curve.
During key generation when importPkcs8 is absent, the default is "P-256". During key import when importPkcs8 is specified, this is auto-detected from SPKI.
OptionalimportImport PKCS#8 private key and SPKI public key instead of generating.
If curve is also specified, it must match the SPKI public key.
Key generation parameters.