Recent work on key establishment for sensor networks has shown that it is feasible to employ limited Elliptic Curve Cryptography in sensor networks through hybrid protocols. In this paper, we propose a hybrid key establishment protocol for uniform self-organized sensor networks. The proposed protocol combines the Elliptic Curve Diffie-Hellmann key establishment with implicit certificates and symmetrickey cryptographic techniques. The protocol can be implemented on uniform networks comprised of restricted functional devices. Furthermore, due to its public-key nature, the protocol is resilient to a wide range of passive and active attacks such as known-key attacks, as well as attacks against the confidentiality, integrity and authenticity of the communication. The protocol is scalable and efficient for low-capability devices in terms of storage, communication and computational complexity: the cost per node for a key establishment is reduced to one scalar multiplication with a random point plus one with a fixed point.