Ad hoc networks have many features that make them attractive for the use in many applications. However, there are many unsolved problems in ad hoc networks; securing the network being one of the major concerns. The dynamic and cooperative nature of ad hoc networks present substantial challenges in securing these networks. In this paper, we focus on the role of Certification Authorities (CAs) in securing ad hoc networks communication. We introduce the concept of certification authorities and their selection, we survey and classify the certification schemes and give a brief overview on the revocation schemes. We conclude and end this paper by discussing some challenges and research issues in the certification and revocation in ad hoc networks.