As a team lead in a large IT company, I regularly do "first contact" calls with applicants. I always, of course, ask about what kind of money they intend to make. I cannot remember anyone ever denying that information to me. Nor did I ever receive a number which made me rub my hands in glee because I'd be getting an ultra cheap awesome employee.
I do not ask that to fix the high limit of your eventual salary, or to swindle them out of a good salary, but because it is an important information. At the end of the day, both the applicant and me want to arrive at a proper salary. Getting good people is very expensive; I simply cannot afford to lose someone over a too-low salary. These days, everybody has the same information, and everybody roughly knows what's a proper range.
Also, if you come with a number which is incredibly high, we can quickly end the process - there is no use talking for hours if it is clear that your conception of your salary is wildly different from what I'm willing or able to pay.
Finally, if in my mind they are worth 50.000,-, but they say 100.000,-, this is an indication that there might well be a severe misunderstanding either about their skill or experience, or about what the position entails. In such a case, I won't argue about the price, but will try to find out what's going on.
So my advice would be to absolutely give a number. Figure out the proper range for a salary, taking into consideration your graduation, skills, experience and so on. Go with the upper limit of the range, and if you wish, add a percentage as a buffer.
Feel free to say something like "I did some market research, and I believe up to XXX would be a proper salary." Or, if you don't worry about giving out that info, "I am getting roughly XXX now and would expect more than that." Or simply "I'd expect not much less than XXX." All are quite un-attackable statements. I couldn't care less whether they are true or false. It's simply a piece of information. Yes, except in very rare circumstances your chances of getting more than what you said are very low, but I trust most people are able to figure out a relatively realistic high limit.
If, during further talks, it turns out that the position you are applying for is different from what you envisioned, you can also of course adjust your statement about the salary; there is nothing legally binding about your first number. You should be pretty sure not to do that out of a whim, or you could come over as fickle. Reserve that option for when it really counts.