For all versions prior to 3.3, there is no encryption done specifically on the contents being transferred. Furthermore, since it doesn’t use REST or Bolt, there is no SSL/https configuration either. Transactions are propagated via transaction logs, which are a binary representation of the data and are not human-readable. However, that does not equate to encryption.

A common way to solve this problem is to implement VPN tunneling between instances, such that the data is transferred through a secure tunnel.

Commencing with 3.3 we would recommend Intra-Cluster Encryption