I think you might have a hard time at this finding an attack that is worthy of a Master's Thesis. For this I think you would need to find your own attack or at least your own variant, and sounds like a very hard to do. It might be possible... but I would look at other options then an attack.
Before you get to far in this have you thought about instead of an attack looking at using a study of "Blockchain". It is kinda all the rage to use "Blockchain" technology when someone launches something that want's investors anymore. It is something if you had a good thesis in you might be able to use to help get a job. I think a thesis in "Blockchain" is going to be much more achievable on a master's level then a attack unless you are very talented at finding exploits.
Thanks for your reply, Could you please provide me a link to a paper or some article , so I can have a much clearer view as to what you are suggesting