In wireless ad hoc networks, most of the authentication protocols assume a single source of trust. However, in the presence of multiple trust sources (called source group in this chapter), it becomes difficult to design resource- (or energy-) efficient authentication protocols, especially for multicast/broadcast services, utilizing multiple trust sources at the same time. Some traditional authentication approaches may be extended and used for this purpose. However, the communication overhead, for example, may increase significantly in proportion to the number of trust sources. In this chapter, we propose a new scheme named as Multi-Source Authentication with Split-Join One-Way Key Chain (SOKC). In this new technique, the communication overhead is small and constant, and the memory requirement at the verifier node is also minimal. The source group node needs to store n keys, where n represents the key chain length, which may be a reasonable requirement considering that the trust sources usually have more resources compared to other regular node(s) in the network (e.g., base stations in wireless sensor networks).