This problem has plagued the original XBOX hacking community ... If you would like to read it, it’s free and worth your time. As for open-source modchips, they rule, and it’s not the first ...

[Paul] let me know about a new way to get a hacked kernel on a XBox 360. A new timing attack will soon allow you to install an older kernel with without having the CPU key which was the catch 22 ...