Configuration :: Custom Config Files Encryption

I have a couple of configuration files flxConnection.config and flxSecurity.config files which are being referenced from the Machine.config file like below.

<securitySettings configSource="flxSecurity.config" />
<connectionStrings configSource="flxConnection.config" />

I would like to encrypt the files (a) flxSecurity.config and (b) flxConnection.config using the RSAProtectedConfigurationProvider using a custom RSA key, which can be deployed to other servers. How is that possible? If possible, looked at a variety of stuff in the internet and they all seem to be referring to either Web.config or Machine.config encryption which is pretty straight-forward. This is how the flxConnection.config looks like,

<?xml version="1.0"?>
<connectionStrings>
<add name="LocalSqlServer" connectionString="data source=.SQLEXPRESS;Integrated
Security=SSPI;AttachDBFilename=|DataDirectory|aspnetdb.mdf;User Instance=true"
providerName="System.Data.SqlClient" />
</connectionStrings>

This is how the flxSecurity.config looks like,

<?xml version="1.0" encoding="UTF-8"?>
<securitySettings>
<add key="APC_APP_ID" value="apcrpt"/>
</securitySettings>