Security services such as authentication and pair wise key establishment are critical in sensor networks. They enables sensor nodes to communicate securely with each other. Mobile sinks are useful in many wireless sensor network applications for data accumulation and localized sensor reprogramming. In the key management scheme, an attacker can easily obtain a large number of keys by capturity a small fraction of the sensor nodes. This paper describes an efficient security algorithm that allows the use of any pair wise key predistribution scheme as its basic component.