If passwords are used for authentication, PostgreSQL must transmit only encrypted representations of passwords.
The DoD standard for authentication is DoD-approved PKI certificates.
Authentication based on User ID and Password may be used only when it is not possible to employ a PKI certificate, and requires AO approval.
In such cases, passwords need to be protected at all times, and encryption is the standard method for protecting passwords during transmission.
PostgreSQL passwords sent in clear text format across the network are vulnerable to discovery by unauthorized users. Disclosure of passwords may easily lead to unauthorized access to the database.