auth.js

var whr = new ActiveXObject("WinHttp.WinHttpRequest.5.1");
var doc = new ActiveXObject("Msxml2.DOMDocument");
var utf8 = new ActiveXObject("System.Text.UTF8Encoding");

whr.Open("GET", "https://radiko.jp/v2/api/auth1", false);
whr.SetRequestHeader("X-Radiko-App", "pc_html5");
whr.SetRequestHeader("X-Radiko-App-Version", "0.0.1");
whr.SetRequestHeader("X-Radiko-User", "dummy_user");
whr.SetRequestHeader("X-Radiko-Device", "pc");
whr.Send();

var token = whr.GetResponseHeader("X-Radiko-AuthToken");
var length = whr.GetResponseHeader("X-Radiko-KeyLength");
var offset = whr.GetResponseHeader("X-Radiko-KeyOffset");

var authkey = "bcd151073c03b352e1ef2fd66c32209da9ca0afa";
var part = authkey.substr(offset, length);
var element = doc.createElement("base64");
var bytes = utf8.GetBytes_4(part);
element.dataType = "bin.base64";
element.nodeTypedValue = bytes;
var partialkey = element.text;

whr.Open("GET", "https://radiko.jp/v2/api/auth2", false);
whr.SetRequestHeader("X-Radiko-AuthToken", token);
whr.SetRequestHeader("X-Radiko-PartialKey", partialkey);
whr.SetRequestHeader("X-Radiko-User", "dummy_user");
whr.SetRequestHeader("X-Radiko-Device", "pc");
whr.Send();

WScript.Echo(token + " " + whr.statusText);