Encryption Mechanisms Overview

Data at rest and data in transit encryption function at different technology layers of the cluster:

Layer Description
Application Applied by the HDFS client software, HDFS Transparent Encryption lets you encrypt specific folders contained in HDFS. To securely store the required encryption keys, Cloudera recommends using Cloudera Navigator Key Trustee Server in conjunction with HDFS encryption. See Enabling HDFS Encryption Using Navigator Key Trustee Server for details.

Data stored temporarily on the local filesystem outside HDFS by CDH components (including Impala, MapReduce, YARN, or HBase) can also be encrypted. See Configuring Encryption for Data Spills for details.

Operating System At the Linux OS filesystem layer, encryption can be applied to an entire volume. For example, Cloudera Navigator Encrypt can encrypt data inside and outside HDFS, such as temp/spill files, configuration files, and databases that store metadata associated with a CDH cluster. Navigator Encrypt requires a license for Cloudera Navigator and must be configured to use Navigator Key Trustee Server.
Network Network communications between client processes and server processes (HTTP, RPC, or TCP/IP services) can be encrypted using industry-standard TLS/SSL as detailed in Encrypting Data in Transit.

Here are some good starting places for more information about encryption for Cloudera clusters: