What ciphers are supported for spark internode communication?

https://spark.apache.org/docs/3.1.2/security.html#encryption

Property name: spark.network.crypto.config.*
Default: None
Meaning: Configuration values for the commons-crypto library, such as which cipher implementations to use. The config name should be the name of commons-crypto configuration without the commons.crypto prefix.

This description is superficial.

What will happen in case of None? What ciphers are supported?