Recent technology advances in low-cost, low-power chip design have made the deployment of large-scale sensor networks economically feasible. Data forwarding algorithms and protocols have been among the first set of issues explored in sensor networking. The primary goal of current routing protocols for wireless sensor network is to improve the energy efficiency while guarantee the required communication. Hence these protocols take security as an optional. Security problems exist in such protocols that may be vulnerable to various attacks and cannot be applied to many fields. Several energy-conserving security architectures have been proposed in wireless sensor networks where Key distribution and Key management mechanism are basic problem of them. RSA, DSA and Elliptic curve cryptography (ECC) are three most widely adopted cryptosystems. ECC is considered as the one which has the highest security quality in per bit key among current public key cryptosystems. Security is not the only attractive feature of Elliptic Curve Cryptography (ECC), it also computationally more efficient than the first generation public key systems like RSA and Diffie-Hellman. This paper is to understand the threats in WSNs and try to present a unique secure node authentication scheme with strong and efficient key management scheme.