Is it haram to use unused power of a computer without permission?

Assalamualaikum, I am a hacker, but I do not want to use any of my skills to do anything that is haram. I would like to know if it is haram to use use the *remaining* **unused** power of a person's computer(*without his permission*) to help do some calculations? Note that this person is barely going to lose anything and half of any profit that I get from this will already go to charity. Should I do this or abandon the whole idea?