In this paper, the authors propose time synchronized one-time-password scheme to provide secure wake up authentication. The main constraint of wireless sensor networks is their limited power resource that prevents the user from using radio transmission over the network to transfer the passwords. On the other hand computation power consumption is insignificant when compared to the costs associated with the power needed for transmitting the right set of keys. In addition to prevent adversaries from reading and following the timeline of the network, they propose to encrypt the tokens using symmetric encryption to prevent replay attacks.