java-docs-samples\iot\api-client\manager\src\main\java\com\example\cloud\iot\examples\MqttExample.java from: KeyFactory kf = KeyFactory.getInstance("ES256"); to: KeyFactory kf = KeyFactory.getInstance("EC"); EC is the right name for the Elliptic Curve algorithm. https://docs.oracle.com/javase/8/docs/technotes/guides/security/StandardNames.html#KeyFactory