The significance of NP-Hard Problems in Cryptography I didn't refer any literature but thought this was ideal to get views from people here..

Assuming that P=NP is proved would cryptography(only provable security) be impossible? Since the adversary can break any scheme in polynomial time.

Aren't the NP-hard problems enough to save the day? I've heard of crypto-systems based on "subset problems". Since P=NP would not affect the nature of NP-hard problems.

It would also be great if can suggest any interesting articles regarding this..

Thanks!

P.S: Please feel free to edit if you find any naive statements in the question.
Hardness of NP-complete problems is not sufficient for cryptography.  Even if NP-complete problems are hard in the worst-case (P≠NP ), they still could be efficiently solvable in the average-case. Cryptography assumes the existence of average-case intractable problems in NP. Also, proving the existence of hard-on-average problems in NP using the $P \ne NP$ assumption is a major open problem.

An excellent read is the classic by Russell Impagliazzo, A Personal View of Average-Case Complexity, 1995. 

An excellent survey is Average-Case Complexity by Bogdanov and Trevisan, Foundations and Trends in Theoretical Computer Science Vol. 2, No 1 (2006) 1–106