Mobile ad-hoc networks (MANETs) provide the technical platform for efficient information sharing in emergency and rescue operations. Some the data present on the scene is highly confidential and requires protection. However, one of the main threats to a network is insertion of false data or alteration of existing ones, which could easily lead to network disruption and, ultimately, cause loss of human lives. This paper presents a simple and efficient key management protocol, called SKiMPy. The protocol allows devices carried by the rescue personnel to establish a symmetric shared key, to be used primarily to perform message signatures. The protocol is designed and optimized having in mind the high dynamicity present in such a scenario. Two different implementations were made, first as a standalone application and later as a plugin for the Optimized Link State Routing Protocol (OLSR). We present the evaluation results for both implementations and, in addition, for the latter one we describe in detail the emulation platform developed to test and evaluate this and other MANET protocols.