var hex1 = "B1C85C061C98E713DEF0E2EDDDDB432738674C9F8962F09B75E943D55F9FB39F";
var hex2 = "121B0D3327A21B8048FC7CA6FD07AACC0D8DF59B99DB098686696573E3686E6C";
var result = hex1 ^ hex2; //XOR the values
console.log(result); // outputs: 0 which does not sound good.
parseInt(hexString, 16) your hex string before. Specifically in your case this wouldn't work because your hex is to big for a number. You would have to create your own customized XOR function.
Take a look at this link: How to convert hex string into a bytes array, and a bytes array in the hex string?
The resulting bytearray will be ellegible for a manual XOR. Byte by byte. Maybe this will help: Java XOR over two arrays.