static EcdsaParameters.CurveType getCurveType(JwtEcdsaParameters parameters)
      throws GeneralSecurityException {
    if (parameters.getAlgorithm().equals(JwtEcdsaParameters.Algorithm.ES256)) {
      return EcdsaParameters.CurveType.NIST_P256;
    }
    if (parameters.getAlgorithm().equals(JwtEcdsaParameters.Algorithm.ES384)) {
      return EcdsaParameters.CurveType.NIST_P384;
    }
    if (parameters.getAlgorithm().equals(JwtEcdsaParameters.Algorithm.ES512)) {
      return EcdsaParameters.CurveType.NIST_P521;
    }
    throw new GeneralSecurityException("unknown algorithm in parameters: " + parameters);
  }
This key manager produces new instances of {@code JwtEcdsaVerify}. It doesn't support key
generation.
java_src/src/main/java/com/google/crypto/tink/jwt/JwtEcdsaVerifyKeyManager.java