This paper presents the ECCE Protocol, a new distributed, probabilistic, cooperative protocol to establish a secure pair-wise communication channel between any pair of sensors in aWireless Sensor Network (WSN). The main contribution of the ECCE Protocol is to allow the set up of a secure channel between two sensors (principals) that do not share any pre-deployed key. This feature is obtained involving a set of sensors (cooperators) in the channel establishment protocol. Further, the security provided by the protocol is adaptive with the level of threat in the WSN, that is, the higher the security threat, the more cooperators can be involved to enhance the resiliency of the channel. We provide extensive simulations of the proposed scheme, which show that ECCE increases both the probability of a secure channel set up and the probability of channel resilience with respect to other protocols.