private static final ECParameterSpec toParameterSpec(EciesParameters.CurveType curveType)
      throws GeneralSecurityException {
    if (curveType == EciesParameters.CurveType.NIST_P256) {
      return EllipticCurvesUtil.NIST_P256_PARAMS;
    }
    if (curveType == EciesParameters.CurveType.NIST_P384) {
      return EllipticCurvesUtil.NIST_P384_PARAMS;
    }
    if (curveType == EciesParameters.CurveType.NIST_P521) {
      return EllipticCurvesUtil.NIST_P521_PARAMS;
    }
    throw new GeneralSecurityException("Unsupported curve type: " + curveType);
  }
This key manager generates new {@code EciesAeadHkdfPrivateKey} keys and produces new instances of
{@code EciesAeadHkdfHybridDecrypt}.
java_src/src/main/java/com/google/crypto/tink/hybrid/EciesAeadHkdfPrivateKeyManager.java