Use AES by default for HDFS wire encryption

[Jimvin]

When Kerberos is enabled the operator automatically enables wire encryption by setting dfs.data.transfer.protection to "privacy" and dfs.encrypt.data.transfer to "true". By default the 3DES algorithm is used, but the faster and more secure AES algorithm is available. There is a marked performance improvement when AES is enabled compared to 3DES.

AES encryption can be enabled by adding the following property to hdfs-site.xml:

• dfs.encrypt.data.transfer.cipher.suite: "AES/CTR/NoPadding"

The key length can be defined using the property dfs.encrypt.data.transfer.cipher.key.bitlength to 128, 192 or 256, with 128 bit being the default.

https://hadoop.apache.org/docs/r3.3.6/hadoop-project-dist/hadoop-common/SecureMode.html#Data_Encryption_on_Block_data_transfer.