The way it's implemented on bitadress currently, it will generate a private key for you. For us who like to generate our own private key (outside of bitadddress), but still would like to split it using their site, there is a fix described here: https://bitcointalksearch.org/topic/m.8041834
Thanks! ssss seems to like a good software. And, I will give this a try!
Under "splitKey: function" replace the line:
var key = new Bitcoin.ECKey(false)
with this line:
var mykey = document.getElementById("combineinput").value.replace(/^\s+|\s+$/g, "").toString();
if ("combineinput" == "") {var key = new Bitcoin.ECKey(false)} else {var key = new Bitcoin.ECKey(mykey)};
Now you can enter your private key into the box under "Enter Available Shares (whitespace separated)" and press the generate button. If you leave the box empty it will generate (and split) new private key.
~~MZ~~