© 2016 IEEE. Handling the security in Wireless Sensor Networks (WSNs) requires cryptographic mechanisms to detect faulty and unstable nodes that lead to the inactivity of network during packet travelling. Although, cryptographic security mechanism operations demand a high calculation of computational time and memory resources, while the sensor nodes have low memory and low computation capability. Alternatively, trust management schemes are tools to address some main issues in WSNs including memory and storage space, key generation, and re-keying. In this work, we will present solution of memory resources consumption and key management processing issues for a secure maritime coastal monitoring system. This system is a symmetric security scheme with a dynamic update key based on a trusted node configuration, called a leader node, which works as a trusted third party.