if you want to work in the context of European Research, this report: http://cordis.europa.eu/fp7/ict/ssai/docs/cloud-report-final.pdf provides quite an exhaustive list
Cloud security Issues are always a hot topic. You can select Security issues in cloud computing discuss about problems, issues, and concerns. Good Luck!!
if you want to work in the context of European Research, this report: http://cordis.europa.eu/fp7/ict/ssai/docs/cloud-report-final.pdf provides quite an exhaustive list
In cloud PaaS, SaaS and IaaS are basic model but now Security as a Service and Network as a Service are new services and may be you get find other. So, as per your interest you can go for only networking side, Vitalization or with security as well.
It depends on which angle (within cloud as a provider or outside cloud as a client) you are going to look into and which level (low vs. high) you are interested in.
For example, if within cloud as a provider, you can look into how to isolate VMs if you are interested in low level programming, or global level resource allocation if you are good at math;
From cloud clients viewpoint, you can look into data security and privacy issues if you are good at math; or you can design and develop better way to help clients better (deply and manage) their applications onto the cloud.
Anyway, there are a lot of interesting thingsto do in this area.