How to store credentials for FTP connection in a secure and configurable way? The credentials changes from one env to another

I have a workspace which reads files from an SFTP location. I am using FTPCaller to connect to the SFTP. The credentials will change depending on the env i.e. different creds for dev, qa and prod.

What is the best way to store credentials for the SFTP connection? Right now, I have these in a config file stored in Resources>Data. My workspaces reads this into a variable and then uses it to connect to the SFTP.

However, this is not safe since:

1. credentials are stored in plaintext in the config file
2. they also get printed in the log like every other property from that file.