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A ROM-friendly secure code update mechanism for WSNs using a stateful-verifier τ-time signature scheme

Several mechanisms have been proposed to efficiently authenticate multicast of finite data streams as needed for code image updates in wireless sensor networks (WSNs). They involve either a public-key digital signature or loose time synchronization between the sender and the receivers. What usually does not get any attention is the program memory (ROM) occupied by these mechanisms which do not fulfill the primary task of a sensor network.
 An optimized implementation of the elliptic curve digital signature scheme occupies up to 25% of the ROM of a TelosB node; the same or even more is needed for time synchronization schemes. Therefore, if sensor networks do not need public-key operations or time synchronization for their primary task, these SCU mechanism are not suitable for coexistence with the application code on the sensor nodes. This work contributes in two directions. Firstly, we propose a stateful-verifier T-time signature scheme based on Merkle's one-time signature. Secondly, we propose a protocol exploiting our signature scheme for securing existing code image update protocols for WSNs minimizing ROM overhead to 1% on TelosB motes.