Security in a mobile ad hoc network is maintained by using various forms of encryption, various encryption schemes, and various multi-phase keying techniques. In one configuration, an over the air, three-phase, re-keying technique is utilized to ensure that no authorized nodes are lost during re-keying and that nodes that are intended to be excluded from re-keying are excluded. In another configuration, an over the air, two-phase keying technique, is utilized to maintain backwards secrecy.