Keystores and the Key Management Server

Integrating HDFS with an external, enterprise-level keystore is the first step to deploying transparent encryption. This is because separation of duties between a key administrator and an HDFS administrator is a very important aspect of this feature.

However, most keystores are not designed for the encrypt/decrypt request rates seen by Hadoop workloads. This led to the development of a new service, called the Key Management Server (KMS), which serves as a proxy between HDFS clients and the backing keystore. Both the keystore and KMS must use Hadoop's KeyProvider API to interact with each other and with HDFS clients.

While HDFS encryption can be used with a local Java KeyStore for key management, Cloudera does not recommend this for production environments where a more robust and secure key management solution should be used. Cloudera offers the following two options for enterprise-grade key management:

• Key Trustee Server is a key store for managing encryption keys. To integrate with the Key Trustee Server, Cloudera provides Ranger KMS.
• Hardware security modules (HSM) are third-party appliances that provide the highest level of security for keys.

The diagram below illustrates how HDFS clients and the NameNode interact with an enterprise keystore through the Key Management Server. The keystore can be either the Key Trustee Server or a support HSM.