I'm looking for a good reference, possibly a survey, on the different types of cryptography methods. As far as I understand, the security of a cryptographic method depends on some hardness assumptions, and I've heard of methods based on the hardness of factorization, discrete logarithm, NP-complete problems (such as the Knapsack problem) and problems on lattices.
Is there any good text addressing the different existing paradigms?
In particular, I would be interested on open problems and questions on less studied methods.
Answers for this question may include both references to a text giving an overview of the area but also to specific methods.