C4W: An Energy Efficient Public Key Cryptosystem for Large-Scale Wireless Sensor Networks

Abstract

With hardware support and software optimization, Public Key Cryptography (PKC) has been announced feasible on micro sensors recently [1][2][22][23]. A number of experiments proved that the Elliptic Curve Cryptography (ECC) is more suitable for resource constraint motes compared with RSA [2][3]. But even ECC based protocols still cost too much energy. In this paper, we propose C4W, an identity-based public key infrastructure specially designed for wireless sensor networks (WSNs), in which all nodes can generate others' ECC public keys directly from their identities. Without certificates, no energy will be consumed for certificates communication and verification, which makes C4W especially energy efficient. C4W uses a protocol without certificates to realize mutual authentication and key agreement. Compared with a simplified SSL (SSSL) protocol using an abbreviated certificate, C4W consumes lower than 35% energy, and the communication consumption of C4W is only 28.5% of that consumed by SSSL. Furthermore, the energy analysis of C4W illuminates that the expensive public key computational cost is almost neglectable compared with the heavy communication consumption in a large-scale WSNs, which gives the asymmetric key management in WSNs a bright future.