very impressed article about how to do 2-2 mulit-sig keys. I was thinking 2/3 of threadholding key sign before. But I was wrong, because the idea of 2/3 comes from the traditional client-bank-gov sign that bank & gov can just transfer or lock all of client's fund and act as a judger.

bitcoin should delete the gov and any way to skip client and rob the funds. However, we do need mediator(wallet such as). So, a 2-2 solution could be eough to control the mediator and holding the key by client theirselves!