This is a user-friendly version of Groestlcoin Core's python script for generating an RPC Auth config string. For additional security you can save this web page locally and run it on an offline computer.
The Groestlcoin Core RPC Auth Generator repository can be found at https://github.com/groestlcoin/groestlcoin-core-rpc-auth-generator
Twitter Bootstrap: http://getbootstrap.com/