Balancing security and energy consumption in wireless sensor networks

Appling security to messages traveling over wireless links in sensor nodes requires additional energy. This paper describes our suggestions on balancing the level of security and energy consumption based on our measurements using CrossBow and Ember sensor nodes. It was found that the node microcontroller's CPU operates for substantially longer times for both hashing and encryption operations compared to the time for handling messages without any security. However, this has little overall impact on energy consumption. The longer high-power radio transmission times due to hashing were especially costly. For the full operational mode, with CPU processing and also radio transmission of messages, our results indicate that the lifetime of a transmitting node in a security regime is only about one-half of the lifetime without security. Hence, we provided design guidelines to apply security with energy consideration for WSN. They include 2 to 8 bytes MACs for integrity and authentication instead of SHA-1, and the size of messages should match the steps of encryption algorithms.