Many Wireless Sensor Networks are composed of nodes that are virtually identical, i.e. they are clones of one another. The classic “identity” definition cannot properly capture this notion. Even if each node contains an artificial serial number, there is no unique property…no DNA to distinguish devices. Still, all sensor networks must capture some identity notions; code integrity being one such notion. This chapter investigates sensor network node identity relative to the functional properties reflected in executing code found on small computing sensors. We show how wireless sensor networks can establish an important identity property of ensuring code integrity through the process of remote attestation.