I can tell you from experience that usually there's not any written/formal publication requirement but I've never seen anyone getting his PhD in CS without at l

I can tell you from experience that usually there's not any written/formal publication requirement but I've never seen anyone getting his PhD in CS without at least 1 international publication (conference paper not workshop). I disagree with people commenting that you could earn your PhD with zero publication. You need to compare your work with the state of the art and confront other people in conferences this is what research is about and not simply working on something and never open your work to critics. In other theoretical field it's different but in CS there are plenty of opportunity to publish your work. PhD symposiums, poster sessions, workshops and millions of conferences (with probably only 10/20% of very good ones). So even if there's no formal requirement, I'd really suggest you put some effort into it. It's not just for the sake of showing who has the biggest (publication list), it's really to make you interact with people and have an objective opinion on your work through the review process of your submission to conferences. I personally got my PhD with 11 publications (4 top tier conferences) and 5 patents. I can tell you it was a big shock when I submitted my 1st paper and got demolished but I really got valuable feedback I was on the wrong track and my advisor didn't care ;)