We develop a new secure and energy-efficient communication model for the Constrained Application Protocol (CoAP), a light-weight communication protocol designed for smart object networks. This architecture and the communication model ensures data integrity and authenticity over a multi-hop network topology. It provides a mirroring mechanism that uses a proxy to serve data on behalf of sleeping smart objects, thereby allowing them to act as always-online web servers. A working prototype implementation of the architecture is also developed. The security features in the architecture presented in this paper are based on using strong public-key cryptography. Contrary to popular belief, our performance evaluation shows that asymmetric public-key cryptography can be implemented on small 8-bit microcontrollers without modifying the underlying cryptographic algorithms using public libraries.