Protocols for key management are compared and evaluated from the point of view on mobile ad hoc networks (MANET). The issues of fault-tolerance and efficiency of key distribution protocols for group communications in MANET are addressed. Most key distribution protocols existing today are primarily designed for wire-line networks. These protocols either fail to work as intended or cannot work at all when they are applied to the demanding environment of MANET. Parameters and performance of different protocols are analyzed, and then a flat is given out, on which new protocols or existing ones are designed and modified, so that they can be robust, scalable and efficient in MANET.