Historically, information security in the form of secrecy, integrity, and authentication is applicable for any personal computer systems and information dissemination networks. Domains of the networking technologies and security requirements are complex these days. Wireless sensor network depicts a new computing class consisting of large numbers of resource-constrained nodes which are often embedded in their operating environments, distributed over wide geographic areas, or located in remote and largely inaccessible regions also faces the security problem. Lots of security solutions has been made available for wired networks which can also be used for wireless networks, but because of low form factor properties of wireless nodes which are also mobile, it is infeasible to deploy the complex security solutions for wireless networks. In WSNs, challenges such as wireless nature, low battery power and mobility are prime reasons why we are not able to deploy complex security solutions. Hence it is important to study, design and analyse security solutions for this kind of networks. Therefore, the concept of Cryptography Assistant is introduced, which is a highly powered device compared to sensor node. The crypto assistant node is capable of implementing high end cryptography algorithm. This paper mainly focused on energy and time trade-off of encryption algorithms and files communication. Based on the trade-off it can be decided whether encryption can be done by powerful assistant node or by mobile node itself. The algorithms used for implementation are Symmetric algorithm (AES), Asymmetric algorithm (RSA) & Message digest (SHA 512). The results have proved that to make use of cryptography Assistant node for the encoding of information as it consumes less energy and time for encryption.

AES; Cryptography Assistant; RSA; SHA; WSN