The ECC key.
NIST Curve Notes
Keys for use with the secp256r1, secp384r1, and secp521r1 curves are made up of a number of individual parameters.
The public key consists of the following parameters:
The private key consists of one value:
Curve25519 and Curve448 Notes
Keys for use with Curve25519 or Curve448 are made up of a private key and public key field.
XPk holds the public key.
XSk holds the private key.