Apache Argus (previously Ranger) provides data security for a Hadoop cluster by enabling fine-grained access control over Hadoop and related components. It does not yet feature built-in data encryption. Currently a third party add-on is necessary for data protection. For an in-depth look at Argus, including some experiments with the HDP 2.1 Sandbox, check out this blog post: Securing Your Datalake With Apache Argus.
The Knox Gateway provides authentication and access controls for Hadoop. It does not encrypt any stationary data, it only makes use of encryption over the wire. Learn more about using Knox from Hortonworks’ tutorial, Securing your Hadoop Infrastructure with Apache Knox.