Your current settings:
cipher AES-256-CBC
keysize 256
Should do the trick to use 256 bit encryption. You could add
auth sha256
to even use sha256 for authentication. (HMAC) This way you are building an enforced cryptosetup with high crypto in your entire system, for both data- and control-channel.
The other option is to use the directive
tls-cipher [ciphersuite]
in both client and server-config.
Openvpn shows you the available options via
openvpn --show-tls
And then ofcourse pick one of the 256 bit options 😉
