static NistCurvesHpkeKemPrivateKey fromBytes(
      byte[] privateKey, byte[] publicKey, EllipticCurves.CurveType curveType)
      throws GeneralSecurityException {
    EllipticCurves.validatePublicKey(
        EllipticCurves.getEcPublicKey(
            curveType, EllipticCurves.PointFormatType.UNCOMPRESSED, publicKey),
        EllipticCurves.getEcPrivateKey(curveType, privateKey));
    return new NistCurvesHpkeKemPrivateKey(privateKey, publicKey);
  }
Private keys used in Diffie-Hellman-based P256, P384 and P521 HPKE KEM variants.
java_src/src/main/java/com/google/crypto/tink/hybrid/internal/NistCurvesHpkeKemPrivateKey.java