To recover damages under section 10(b) of the securities exchange act and the corresponding sec rule 10b-5, a buyer or seller of a security must prove:

For action brought under Section 10(b)
1.)There was a material misrepresentation or omission
2.) The plaintiff suffered damages
3.) The plaintiff relied on the fraudulent statement and 
4.) existence of scienter
Both 10(b) and 10b-5 cover registered and unregistered securities, and not just original issuances.